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Category:   Device (Firewall)  >   Cisco Firewall Service Module Vendors:   Cisco
Cisco Firewall Service Module Lets Remote Users Deny Service and Potentially Bypass Intended ACLs
SecurityTracker Alert ID:  1017650
SecurityTracker URL:  http://securitytracker.com/id/1017650
CVE Reference:   CVE-2007-0968   (Links to External Site)
Updated:  May 19 2008
Original Entry Date:  Feb 14 2007
Impact:   Denial of service via network, Host/resource access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): prior to 2.3(4.12), 3.1(4)
Description:   A vulnerability was reported in Cisco Firewall Service Module. A remote user can cause denial of service conditions. A remote user may be able to bypass ACLs.

A remote user can send specially crafted data to cause the target device to reload under certain conditions. When verbose logging is enabled and the FWSM processes packets destined to itself, the vulnerability can be triggered.

The vulnerability can be triggered by specific Hypertext Transfer Protocol (HTTP), Secure HTTP (HTTPS), Session Initiation Protocol (SIP), and Simple Network Management Protocol (SNMP) traffic.

Cisco has assigned Cisco Bug IDs CSCsd75794, CSCsg80915, CSCse85707, CSCsg50228, CSCsd91268, CSCsf29974, and CSCse52679 to this vulnerability.

When an authenticated administrator manipulates access control lists (ACLs) that use object groups, the ACL may be corrupted. As a result, traffic intended to be blocked may be permitted and traffic intended to be permitted may be blocked.

Cisco has assigned Cisco Bug IDs CSCse60868 and CSCse99740 to this ACL vulnerability.

Some of these vulnerabilities were reported to Cisco by customers and some were discovered by Cisco.

Impact:   A remote user can cause the target device to reload under certain configurations.

A remote user may be able to gain access to hosts and networks intended to be blocked by the firewall.

Solution:   Cisco has issued fixed versions (2.3(4.12), 3.1(4)), available at:

http://www.cisco.com/pcgi-bin/tablebuild.pl/cat6000-fwsm?psrtdcat20e2

For 2.3(4.12):

http://www.cisco.com/pcgi-bin/tablebuild.pl/FWSMPSIRT?psrtdcat20e2

The Cisco advisory is available at:

http://www.cisco.com/warp/public/707/cisco-sa-20070214-fwsm.shtml

Vendor URL:  www.cisco.com/warp/public/707/cisco-sa-20070214-fwsm.shtml (Links to External Site)
Cause:   Access control error, Exception handling error, State error
Underlying OS:  

Message History:   None.


 Source Message Contents

Date:  Wed, 14 Feb 2007 12:13:07 -0500
Subject:  Cisco Security Advisory: Multiple Vulnerabilities in Firewall Services Module

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1


Cisco Security Advisory: 
Multiple Vulnerabilities in Firewall Services Module

Advisory ID: cisco-sa-20070214-fwsm

http://www.cisco.com/warp/public/707/cisco-sa-20070214-fwsm.shtml

Revision 1.0

For Public Release 2007 February 14 1600 UTC (GMT)

- -----------------------------------------------------------------------

Summary
=======

Multiple vulnerabilities exist in the Cisco Firewall Services Module
(FWSM). These vulnerabilities occur in the processing of specific
Hypertext Transfer Protocol (HTTP), Secure HTTP (HTTPS), Session
Initiation Protocol (SIP), and Simple Network Management Protocol
(SNMP) traffic. If verbose logging is enabled for debugging purposes, a
vulnerability exists when the FWSM processes packets destined to
itself. All of these vulnerabilities may result in a reload of the
device.

An additional vulnerability is included in this advisory in which the
manipulation of access control lists (ACLs) that make use of object
groups may corrupt the ACL and create a situation where unwanted
traffic may be permitted or desirable traffic may be blocked.

These vulnerabilities are independent of each other; a release that is
affected by one vulnerability is not necessarily affected by the
others.

There are workarounds for some of the vulnerabilities disclosed in this
advisory.

Cisco has made free software available to address this issue for
affected customers.

This advisory is posted at 
http://www.cisco.com/warp/public/707/cisco-sa-20070214-fwsm.shtml

Affected Products
=================

The vulnerabilities described in this document
apply to the FWSM. The companion advisory
http://www.cisco.com/warp/public/707/cisco-sa-20070214-pix.shtml
contains information about similar vulnerabilities that affect the
Cisco PIX 500 Series Security Appliances and the Cisco ASA 5500 Series
Adaptive Security Appliances.

Vulnerable Products
+------------------

The following table indicates which software releases for the Cisco
FWSM are affected and under what conditions:

+---------------------------------------------------------------------+
| Vulnerability | Only affected  | Vulnerable | Versions | Cisco Bug  |
|     Name      |     if...      |     by     | affected |     ID     |
|               |                |  default?  |          |            |
|---------------+----------------+------------+----------+------------|
|               | Enhanced       |            |          |            |
| 1. Enhanced   | inspection of  |            | All 3.x  |            |
| Inspection of | HTTP traffic   |            | software |            |
| Malformed     | is enabled     | No         | releases | CSCsd75794 |
| HTTP Traffic  | through the    |            | prior to |            |
| May Cause     | command        |            | 3.1      |            |
| Reload        | "inspect http  |            | (3.24)   |            |
|               | <appfw>"       |            |          |            |
|---------------+----------------+------------+----------+------------|
|               | SIP inspection |            |          |            |
|               | is enabled     |            | All      |            |
|               | through the    |            | software |            |
|               | command "fixup |            | releases |            |
| 2. Inspection | protocol sip"  |            | prior to |            |
| of Malformed  | (in FWSM       | Yes for    | 2.3      |            |
| SIP Messages  | software 2.x   | 2.x and no | (4.12)   | CSCsg80915 |
| May Cause     | and before) or | for 3.x    | and all  |            |
| Reload        | through the    |            | 3.x      |            |
|               | command        |            | releases |            |
|               | "inspect sip"  |            | prior to |            |
|               | (in FWSM       |            | 3.1      |            |
|               | software 3.x   |            | (3.24)   |            |
|               | and later)     |            |          |            |
|---------------+----------------+------------+----------+------------|
|               | Logging at     |            |          |            |
|               | "debugging"    |            |          |            |
| 3. Processing | level          |            | All 3.x  |            |
| of Packets    | (regardless of |            | software |            |
| Destined to   | the logging    | No         | releases | CSCse85707 |
| the FWSM May  | destination)   |            | prior to |            |
| Cause Reload  | and syslog     |            | 3.1(3.3) |            |
|               | message 710006 |            |          |            |
|               | is enabled     |            |          |            |
|---------------+----------------+------------+----------+------------|
|               | Network access |            |          |            |
|               | authentication |            |          |            |
| 4. Processing | is enabled     |            | All 3.x  |            |
| of Malformed  | through the    |            | software |            |
| HTTPS Traffic | "aaa           | No         | releases | CSCsg50228 |
| May Cause     | authentication |            | prior to |            |
| Reload        | match" or "aaa |            | 3.1      |            |
|               | authentication |            | (3.18)   |            |
|               | include"       |            |          |            |
|               | commands       |            |          |            |
|---------------+----------------+------------+----------+------------|
|               | Network access |            |          |            |
|               | authentication |            |          |            |
|               | is enabled     |            |          |            |
| 5. Processing | through the    |            | All 3.x  |            |
| of Long HTTP  | "aaa           | No         | releases | CSCsd91268 |
| Requests May  | authentication |            | prior to |            |
| Cause Reload  | match" or "aaa |            | 3.1(2)   |            |
|               | authentication |            |          |            |
|               | include"       |            |          |            |
|               | commands       |            |          |            |
|---------------+----------------+------------+----------+------------|
| 6. Processing | HTTPS server   |            | All 3.x  |            |
| HTTPS Traffic | is enabled     |            | releases |            |
| May Cause a   | through the    | No         | prior to | CSCsf29974 |
| Reload        | "http server   |            | 3.1      |            |
|               | enable"        |            | (3.11)   |            |
|               | command        |            |          |            |
|---------------+----------------+------------+----------+------------|
|               | SNMP traffic   |            |          |            |
|               | from a         |            |          |            |
|               | particular IP  |            |          |            |
|               | address is     |            |          |            |
| 7. Processing | permitted      |            | All 3.x  |            |
| of Malformed  | through the    |            | releases |            |
| SNMP Requests | command        | No         | prior to | CSCse52679 |
| May Cause a   | "snmp-server   |            | 3.1(3.1) |            |
| Reload        | host           |            |          |            |
|               | <interface     |            |          |            |
|               | name> <IP      |            |          |            |
|               | address of     |            |          |            |
|               | SNMP server>"  |            |          |            |
|---------------+----------------+------------+----------+------------|
|               |                |            | All      |            |
|               |                |            | software |            |
| 8.            | ACL makes use  |            | releases |            |
| Manipulation  | of object      |            | prior to | CSCse60868 |
| of ACL May    | groups and ACL | No         | 2.3(4.7) | and        |
| Cause ACL     | is manipulated |            | and all  | CSCse99740 |
| Corruption    | by an          |            | 3.x      |            |
|               | administrator  |            | releases |            |
|               |                |            | prior to |            |
|               |                |            | 3.1(3.1) |            |
+---------------------------------------------------------------------+

The relationship between the vulnerabilities described in this advisory
and the equivalent vulnerabilities in the Cisco PIX 500 Series Security
Appliances and Cisco ASA 5500 Series Adaptive Security Appliances is
given in the following table. If a vulnerability discussed in this
document is not present in this table, it does not affect the Cisco PIX
500 Series Security Appliances and Cisco ASA 5500 Series Adaptive
Security Appliances.

+-------------------------------------------------------------+
|          Vulnerability          | PIX/ASA Bug  |  FWSM Bug  |
|                                 |      ID      |     ID     |
|---------------------------------+--------------+------------|
| Enhanced Inspection of          |              |            |
| Malformed HTTP Traffic May      | CSCsd75794   | CSCsd75794 |
| Cause Reload                    |              |            |
|---------------------------------+--------------+------------|
| Inspection of Malformed SIP     | CSCse27708   |            |
| Messages May Cause Reload       | and          | CSCsg80915 |
|                                 | CSCsd97077   |            |
+-------------------------------------------------------------+

To determine if you are running a vulnerable version of FWSM software,
issue the "show module" command in IOS or CatOS to identify what modules
and sub-modules are installed in the system.

The example below shows a system with a Firewall Service Module
(WS-SVC-FWM-1) installed in slot 4.

    6506-B#show module
    Mod Ports Card Type                              Model              Serial No.
    --- ----- -------------------------------------- ------------------ -----------
     1   48  SFM-capable 48 port 10/100/1000mb RJ45 WS-X6548-GE-TX     SAxxxxxxxxx
     4    6  Firewall Module                        WS-SVC-FWM-1       SAxxxxxxxxx
     5    2  Supervisor Engine 720 (Active)         WS-SUP720-BASE     SAxxxxxxxxx
     6    2  Supervisor Engine 720 (Hot)            WS-SUP720-BASE     SAxxxxxxxxx


After locating the correct slot, issue the "show module <slot number>"
command to identify the version of software running:

    6506-B#sho module 4
    Mod Ports Card Type                              Model              Serial No.
    --- ----- -------------------------------------- ------------------ -----------
     4    6  Firewall Module                        WS-SVC-FWM-1       SAxxxxxxxxx

    Mod MAC addresses                       Hw    Fw           Sw           Status
    --- ---------------------------------- ------ ------------ ------------ -------
     4  0003.e4xx.xxxx to 0003.e4xx.xxxx   3.0   7.2(1)       2.3(1)       Ok


In this example, the FWSM is running version 2.3(1) as indicated by the
column under "Sw" above.

Note:  recent versions of IOS will show the software version of each
module in the output from the "show module" command so executing the 
"show module <slot number>" command is not necessary.

Alternatively, the information may also be gained directly from the
FWSM through the "show version" command:

    FWSM#show version

    FWSM Firewall Version 2.3(1)


For customers managing their FWSM through the PIX Device Manager (PDM)
or the Cisco Adaptive Security Device Manager (ASDM), log into the
application, and the version may be found either in the table in the
login window or in the upper left hand corner of the PDM/ASDM window
indicated by a label similar to:

FWSM Version: 2.3(1)

Products Confirmed Not Vulnerable
+--------------------------------

With the exception of the Cisco PIX 500 Series Security Appliances and
the Cisco ASA 5500 Series Adaptive Security Appliances, no other Cisco
products are known to be vulnerable to the issues described in this
advisory.

Details
=======

The Cisco Firewall Services Module is a high-speed, integrated firewall
module for Catalyst 6500 series switches and Cisco 7600 series routers.
It offers firewall services with stateful packet filtering and deep
packet inspection.

Multiple vulnerabilities exist in certain versions of the FWSM software
that may cause the device to unexpectedly reload or that may cause
traffic to be permitted or denied contrary to the security policy in
place.

1. Enhanced Inspection of Malformed HTTP Traffic May Cause Reload
+----------------------------------------------------------------

This vulnerability may cause a FWSM to reload when the FWSM performs
enhanced inspection of HTTP requests, and a malformed HTTP request is
inspected by the FWSM. The FWSM only performs enhanced inspection of
HTTP traffic when the command "inspect http <appfw>" is present in the
configuration (appfw is the name of a specific HTTP map.) This command
is disabled by default.

Note:  Enhanced inspection of HTTP traffic is what makes a
configuration affected. Regular inspection of HTTP traffic (through the
command "inspect http" without an HTTP map) will not make a configuration
affected by this vulnerability.

For information on what enhanced inspection of HTTP traffic does, and
how to configure it, please refer to the following URL:

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/mod_icn/fwsm/fwsm_3_1/fwsm_cfg/inspct_f.htm#wp1390330

This vulnerability is documented in Cisco Bug ID CSCsd75794. 


2. Inspection of Malformed SIP Messages May Cause Reload
+-------------------------------------------------------

This vulnerability may cause a FWSM to reload when a malformed SIP
message is received and deep packet inspection of SIP messages is
enabled through the command "fixup protocol sip" (in FWSM software 2.3.x
and before) or through the command "inspect sip" (in FWSM software 3.x
and later). SIP inspection is enabled by default in the 2.3.x series
and before and is disabled by default in the 3.x series and later.

This vulnerability is documented in Cisco Bug ID CSCsg80915. 


3. Processing of Packets Destined to the FWSM May Cause Reload
+-------------------------------------------------------------

This vulnerability will cause the FWSM to reload when trying to
generate syslog message 710006. For this to happen the following two
conditions must be satisfied:

  * The FWSM receives a packet for one of the device's IP addresses and
    the message is not one of the following protocols: TCP, UDP, ICMP,
    OSPF, Failover, PIM, IGMP, and ESP. The source of the packet is not
    relevant.
  * Logging must be enabled at a level high enough to generate syslog
    message 710006. By default this is debugging level (level 7).
    Please note that logging is disabled by default, and Cisco
    recommends customers only log at debugging level for debugging and
    troubleshooting purposes.

    Note:  The documentation for the Cisco Security Monitoring,
    Analysis and Response System (CS-MARS) suggests logging at the
    debugging level so more events can be reported by the firewall.

For more information on syslog message 710006 please refer to the
following document:

  * Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall
    Services Module Logging Configuration and System Log Messages, 3.1
    http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/mod_icn/fwsm/fwsm_3_1/fwsm_log/logmsgs.htm#wp1285757

This vulnerability is documented in Cisco Bug ID CSCse85707. 


4. Processing of Malformed HTTPS Requests May Cause Reload
+---------------------------------------------------------

This vulnerability may cause the FWSM to reload when a user tries to
access a web site and the network administrator has configured the
device to authenticate users before granting them network access. This
feature is known as "authentication for network access", or auth-proxy,
and is enabled through the command "aaa authentication match" or 
"aaa authentication include".

The reload is actually triggered by a specific HTTPS request that is
invalid, and therefore, unlikely to be generated by a regular web
browser.

This vulnerability is documented in Cisco Bug ID CSCsg50228.


5. Processing of Long HTTP Requests May Cause Reload
+---------------------------------------------------

This vulnerability may also cause the FWSM to reload when the
administrator has enabled "authentication for network access
("auth-proxy") through the commands "aaa authentication match" or 
"aaa authentication include". However, in this case, the HTTP request that
causes the reload is valid, although it is not a normal request in the
sense that the URL being requested is very long. A web browser could
potentially generate such a request during regular browsing.

This vulnerability is documented in Cisco Bug ID CSCsd91268. 


6. Processing of HTTPS Traffic May Cause Reload
+----------------------------------------------

This vulnerability may cause a FWSM to reload when the FWSM receives a
particular type of HTTPS traffic directed to the FWSM itself. This is
only a concern when the HTTPS server on the FWSM is enabled through the
command "http server enable". This command is disabled by default.

Cisco is aware of a commercial vulnerability scanner that can generate
the HTTPS traffic that triggers the reload. We are not aware of regular
web browser traffic that triggers this bug.

This vulnerability is documented in Cisco Bug ID CSCsf29974. 


7. Processing of Malformed SNMP Requests May Cause a Reload
+----------------------------------------------------------

This vulnerability may cause a FWSM to reload upon receipt of a
malformed SNMP message from a trusted device. The trusted device must
be allowed explicit SNMP poll access via the command 
"snmp-server host <interface name> <IP of trusted device>".

This vulnerability is documented in Cisco Bug IDs CSCse52679.


8. Manipulation of ACL May Cause ACL Corruption
+----------------------------------------------

This vulnerability may cause access control entries (ACEs) in an ACL to
be evaluated out of order, or not to be evaluated. This ACL corruption
is manifested, besides the obvious traffic implications, when the
output from the "show access-list" command and the corresponding ACL
shown by the "show running-config" command appear to be out of sync. Only
a manual reload of the device will cause this condition to go away.

The ACL corruption occurs when an ACL that makes use of object groups
is manipulated.

This vulnerability is documented in Cisco Bug IDs CSCse60868 
and CSCse99740.


Vulnerability Scoring Details
+----------------------------

Cisco is providing scores for the vulnerabilities in this advisory
based on the Common Vulnerability Scoring System (CVSS).

Cisco will provide a base and temporal score. Customers can then
compute environmental scores to assist in determining the impact of the
vulnerability in individual networks.

Cisco PSIRT will set the bias in all cases to normal. Customers are
encouraged to apply the bias parameter when determining the
environmental impact of a particular vulnerability.

CVSS is a standards based scoring method that conveys vulnerability
severity and helps determine urgency and priority of response.

Cisco has provided an FAQ to answer additional questions regarding CVSS
at http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html.

Cisco has also provided a CVSS calculator to help compute the
environmental impact for individual networks at 
http://intellishield.cisco.com/security/alertmanager/cvss.


CSCsd75794 - Enhanced inspection of Malformed HTTP traffic can crash device 

CVSS Base Score: 3.3
    Access Vector: Remote
    Access Complexity: Low
    Authentication: Not Required
    Confidentiality Impact: None
    Integrity Impact: None
    Availability Impact: Complete
    Impact Bias: Normal

CVSS Temporal Score: 2.7
    Exploitability: Functional
    Remediation Level: Official Fix
    Report Confidence: Confirmed


CSCsg80915 - FWSM - Traceback when inspecting SIP packets

CVSS Base Score: 3.3
    Access Vector: Remote
    Access Complexity: Low
    Authentication: Not Required
    Confidentiality Impact: None
    Integrity Impact: None
    Availability Impact: Complete
    Impact Bias: Normal

CVSS Temporal Score: 2.7
    Exploitability: Functional
    Remediation Level: Official Fix
    Report Confidence: Confirmed


CSCse85707 - FWSM crash when printing debug level syslog 710006

CVSS Base Score: 2.7
    Access Vector: Remote
    Access Complexity: High
    Authentication: Not Required
    Confidentiality Impact: None
    Integrity Impact: None
    Availability Impact: Complete
    Impact Bias: Normal

CVSS Temporal Score: 2.2
    Exploitability: Functional
    Remediation Level: Official Fix
    Report Confidence: Confirmed


CSCsg50228 - FWSM ST MODE crashes at Thread NAME: uauth with RADIUS 

CVSS Base Score: 2.7
    Access Vector: Remote
    Access Complexity: High
    Authentication: Not Required
    Confidentiality Impact: None
    Integrity Impact: None
    Availability Impact: Complete
    Impact Bias: Normal

CVSS Temporal Score: 2.2
    Exploitability: Functional
    Remediation Level: Official Fix
    Report Confidence: Confirmed


CSCsd91268 - FWSM crashes at Thread: uauth while using aaa with TACACS 

CVSS Base Score: 3.3
    Access Vector: Remote
    Access Complexity: Low
    Authentication: Not Required
    Confidentiality Impact: None
    Integrity Impact: None
    Availability Impact: Complete
    Impact Bias: Normal

CVSS Temporal Score: 2.7
    Exploitability: Functional
    Remediation Level: Official Fix
    Report Confidence: Confirmed


CSCsf29974 - Crash in emweb/https thread 

CVSS Base Score: 3.3
    Access Vector: Remote
    Access Complexity: Low
    Authentication: Not Required
    Confidentiality Impact: None
    Integrity Impact: None
    Availability Impact: Complete
    Impact Bias: Normal

CVSS Temporal Score: 2.7
    Exploitability: Functional
    Remediation Level: Official Fix
    Report Confidence: Confirmed


CSCse52679 - FWSM Crash in thread name SNMP

CVSS Base Score: 3.3
    Access Vector: Remote
    Access Complexity: Low
    Authentication: Not Required
    Confidentiality Impact: None
    Integrity Impact: None
    Availability Impact: Complete
    Impact Bias: Normal

CVSS Temporal Score: 2.7
    Exploitability: Functional
    Remediation Level: Official Fix
    Report Confidence: Confirmed




CSCse60868 - Modifying an ACL with an object-group could cause ACL corruption
and 
CSCse99740 - When removing network objects the existing ACL lines are 
		not removed                                  |


CVSS Base Score: 5.3
    Access Vector: Remote
    Access Complexity: High
    Authentication: Not Required
    Confidentiality Impact: Complete
    Integrity Impact: Complete
    Availability Impact: None
    Impact Bias: Normal

CVSS Temporal Score: 4.4
    Exploitability: Functional
    Remediation Level: Official Fix
    Report Confidence: Confirmed


Impact
======

In all cases, with the exception of the "Manipulation of ACL May Cause
ACL Corruption" vulnerability, successful exploitation of any
vulnerability may cause a reload of the affected device. Repeated
exploitation could result in a sustained Denial-of-Service (DoS)
condition.

In the case of the "Processing of Long HTTP Requests May Cause Reload"
vulnerability (CSCsd91268), the reload occurs because a stack-based
buffer is overflowed. In this case remote code execution may be
possible.

In the case of the "Manipulation of ACL May Cause ACL Corruption"
vulnerability, a device that becomes affected after an administrator
manipulates an ACL with object groups may allow traffic that would
normally be denied, or would deny traffic that would normally be
permitted. If the ACL is used for other functions like NAT (policy NAT
and NAT exemption), AAA (auth-proxy), control of access to the device
(SSH, Telnet, HTTP, ICMP), then those functions may be adversely
affected as well.

Software Version and Fixes
==========================

When considering software upgrades, also consult
http://www.cisco.com/go/psirt and any subsequent advisories to determine
exposure and a complete upgrade solution.

In all cases, customers should exercise caution to be certain the
devices to be upgraded contain sufficient memory and that current
hardware and software configurations will continue to be supported
properly by the new release. If the information is not clear, contact
the Cisco Technical Assistance Center ("TAC") or your contracted
maintenance provider for assistance.

Each row of the FWSM software table (below) describes one of the
vulnerabilities described in this document. For each vulnerability the
earliest possible release that contains the fix (the "First Fixed
Release") and the anticipated date of availability for each are listed
in the "First Fixed Release" column. A device running a release that is
earlier than the release in a specific column (less than the First
Fixed Release) is known to be vulnerable. The release should be
upgraded at least to the indicated release or a later version (greater
than or equal to the First Fixed Release label).

+-------------------------------------------------------------+
|          Vulnerability          |    First Fixed Release    |
|---------------------------------+---------------------------|
| 1. Enhanced Inspection of       | 3.1(3.24) (the 2.3.x      |
| Malformed HTTP Traffic May      | series are not affected)  |
| Cause Reload ( CSCsd75794)      |                           |
|---------------------------------+---------------------------|
| 2. Inspection of Malformed SIP  | 2.3(4.12) for the 2.3.x   |
| Messages May Cause Reload (     | series, and 3.1(3.24) for |
| CSCsg80915)                     | the 3.x series            |
|---------------------------------+---------------------------|
| 3. Processing of Packets        | 3.1(3.3) (the 2.3.x       |
| Destined to the FWSM May Cause  | series are not affected)  |
| Reload ( CSCse85707)            |                           |
|---------------------------------+---------------------------|
| 4. Processing of Malformed      | 3.1(3.18) (the 2.3.x      |
| HTTPS Requests May Cause Reload | series are not affected)  |
| ( CSCsg50228)                   |                           |
|---------------------------------+---------------------------|
| 5. Processing of Long HTTP      | 3.1(1.9) (the 2.3.x       |
| Requests May Cause Reload (     | series are not affected)  |
| CSCsd91268)                     |                           |
|---------------------------------+---------------------------|
| 6. Processing HTTPS Traffic May | 3.1(3.11) (the 2.3.x      |
| Cause a Reload ( CSCsf29974)    | series are not affected)  |
|---------------------------------+---------------------------|
| 7. Processing of Malformed SNMP | 3.1(3.1) (the 2.3.x       |
| Requests May Cause a Reload (   | series are not affected)  |
| CSCse52679)                     |                           |
|---------------------------------+---------------------------|
| 8. Manipulation of ACL May      | 2.3(4.7) for the 2.3.x    |
| Cause ACL Corruption (          | series, and 3.1(3.1) for  |
| CSCse60868) and ( CSCse99740)   | the 3.x series            |
+-------------------------------------------------------------+

For the 2.3.x series, FWSM software version 2.3(4.12) contains the
fixes for all the vulnerabilities described in this document.

For the 3.x series, FWSM software version 3.1(4) contains the fixes for
all the vulnerabilities described in this document.

FWSM software is available for download from the following location on
cisco.com:

http://www.cisco.com/pcgi-bin/tablebuild.pl/cat6000-fwsm?psrtdcat20e2

For FWSM release 2.3(4.12) please use the following link:

http://www.cisco.com/pcgi-bin/tablebuild.pl/FWSMPSIRT?psrtdcat20e2

Workarounds
===========

Additional mitigations that can be deployed on Cisco devices within the
network are available in the Cisco Applied Intelligence companion
document for this advisory:

http://www.cisco.com/warp/public/707/cisco-air-20070214-firewall.shtml

1. Enhanced Inspection of Malformed HTTP Traffic May Cause Reload
+----------------------------------------------------------------

It is possible to mitigate this vulnerability by disabling enhanced
inspection of HTTP traffic. Please note that disabling HTTP enhanced
inspection will prevent the FWSM from protecting against specific
attacks and other threats that may be associated with HTTP traffic.
Enhanced inspection of HTTP traffic is disabled by removing the command
"inspect http <appfw>" from the configuration, where appfw is the name of
an HTTP map.

For further information about the "inspect http <appfw>" command, and the
type of checks it performs on HTTP traffic, please see the
documentation for this command at:

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/mod_icn/fwsm/fwsm_3_1/fwsm_ref/i2.htm#wp1570030

Please note that the command "inspect http" (without an HTTP map) can be
left in the configuration and the device will not be affected by this
vulnerability.

2. Inspection of Malformed SIP Messages May Cause Reload
+-------------------------------------------------------

It is possible to mitigate this vulnerability by disabling deep packet
inspection ("fixup" in software version prior to 3.x or "inspect" in
software version 3.x and later) of SIP messages. Note, however, that
this may have negative impact on devices terminating SIP sessions since
SIP traffic will no longer undergo stateful application inspection, and
devices which terminate sessions for this protocol will be exposed to
packets that may cause these devices to crash or become compromised.

If you are running a 3.x FWSM software release, then the alternative is
to allow traffic only from the trusted hosts. The configuration to
accomplish this is as follows:

    access-list sip-acl extended permit udp 10.1.1.0 255.255.255.0 host 192.168.5.4 eq sip
    access-list sip-acl extended permit udp host 192.168.5.4 10.1.1.0 255.255.255.0 eq sip

    class-map sip-traffic
     match access-list sip-acl
    !
    !
    policy-map global_policy
     class inspection_default
      inspect dns maximum-length 512
      inspect ftp
      inspect h323 h225
      inspect h323 ras
      inspect rsh
      inspect rtsp
      inspect esmtp
      inspect sqlnet
      inspect skinny
      inspect sunrpc
      inspect xdmcp
      inspect netbios
      inspect tftp
     class sip-traffic
      inspect sip
    !
    service-policy global_policy global



In this example SIP endpoints are any host within 10.1.1.0 network
(inside the trusted network) and a host with the IP address of
192.168.5.4 (outside of the trusted network). You would have to
substitute these IP addresses with the ones that are used in your
network.

Please note that SIP is an UDP-based protocol, so spoofing SIP messages
is possible.

3. Processing of Packets Destined to the FWSM May Cause Reload
+-------------------------------------------------------------

Since this vulnerability only manifests itself when syslog message
710006 is generated, it is possible to workaround the vulnerability
either by disabling generation of syslog message 710006 altogether, or
by logging at a syslog level that is lower than the syslog level at
which this message is generated.

By default, syslog message 710006 is generated at syslog level 7
("debugging"), so a viable workaround is to log at level 6 or lower.
This can be accomplished with the command "logging <destination> 6". If
syslog message 710006 has been moved to a different logging level, then
the logging level in use must be changed accordingly to prevent the
message from being generated.

If logging at the "debugging" level is necessary, the vulnerability can
also be eliminated by disabling this particular syslog message by using
the command "no logging message 710006".

4. Processing of Malformed HTTPS Requests May Cause Reload
+---------------------------------------------------------

There are no workarounds for this vulnerability.

5. Processing of Long HTTP Requests May Cause Reload
+---------------------------------------------------

There are no workarounds for this vulnerability.

6. Processing HTTPS Traffic May Cause a Reload
+---------------------------------------------

Since this vulnerability is caused by the HTTPS server on the FWSM
failing to handle certain types of HTTPS traffic, disabling the HTTPS
server through the command "no http server enable" is a valid workaround
if this functionality is not needed. Please note that this
functionality is used by ASDM, so if configuration of the FWSM is
exclusively done through ASDM disabling the HTTPS server may not be a
viable workaround.

Additionally, it is possible to limit the exposure by allowing HTTPS
connections only from trusted IP addresses or networks. This can be
accomplished with the "http" command. For example, the following command:

            FWSM(config)# http 192.168.1.10 255.255.255.255 inside



will only permit HTTPS connections from the IP address 192.168.1.10.

7. Processing of Malformed SNMP Requests May Cause a Reload
+----------------------------------------------------------

This bug can only be triggered by a malformed SNMP message that comes
from a device that is allowed SNMP access on the FWSM. If SNMP is not
needed it can be removed through the command 
"no snmp-server host <interface name> <IP address of trusted device>", 
which will eliminate the vulnerability.

8. Manipulation of ACL May Cause ACL Corruption
+----------------------------------------------

There are no workarounds for this vulnerability. However, please note
that the ACL corruption does not occur during normal operation of the
device and it cannot be triggered by some type of traffic. It can only
occur if an administrator makes configuration changes (and more
specifically, if an administrator manipulates an ACL.) For this reason,
if ACL changes are made only during a maintenance window, and the FWSM
is reloaded after making those changes, there should not be any
concerns with this vulnerability.

Obtaining Fixed Software
========================

Cisco will make free software available to address this vulnerability
for affected customers. This advisory will be updated as fixed software
becomes available. Prior to deploying software, customers should
consult their maintenance provider or check the software for feature
set compatibility and known issues specific to their environment.

Customers may only install and expect support for the feature
sets they have purchased. By installing, downloading, accessing
or otherwise using such software upgrades, customers agree to
be bound by the terms of Cisco's software license terms found
at http://www.cisco.com/public/sw-license-agreement.html,
or as otherwise set forth at Cisco.com Downloads at
http://www.cisco.com/public/sw-center/sw-usingswc.shtml.

Do not contact either "psirt@cisco.com" or "security-alert@cisco.com"
for software upgrades.

Customers with Service Contracts
+-------------------------------

Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, this means that upgrades
should be obtained through the Software Center on Cisco's worldwide
website at http://www.cisco.com .

Customers using Third Party Support Organizations
+------------------------------------------------

Customers whose Cisco products are provided or maintained through prior
or existing agreement with third-party support organizations such as
Cisco Partners, authorized resellers, or service providers should
contact that support organization for guidance and assistance with the
appropriate course of action in regards to this advisory.

The effectiveness of any workaround or fix is dependent on specific
customer situations such as product mix, network topology, traffic
behavior, and organizational mission. Due to the variety of affected
products and releases, customers should consult with their service
provider or support organization to ensure any applied workaround or
fix is the most appropriate for use in the intended network before it
is deployed.

Customers without Service Contracts
+----------------------------------

Customers who purchase direct from Cisco but who do not hold a Cisco
service contract and customers who purchase through third-party vendors
but are unsuccessful at obtaining fixed software through their point of
sale should get their upgrades by contacting the Cisco Technical
Assistance Center (TAC). TAC contacts are as follows.

  * +1 800 553 2447 (toll free from within North America)
  * +1 408 526 7209 (toll call from anywhere in the world)
  * e-mail: tac@cisco.com

Have your product serial number available and give the URL of this
notice as evidence of your entitlement to a free upgrade. Free upgrades
for non-contract customers must be requested through the TAC.

Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml
for additional TAC contact information, including special localized
telephone numbers and instructions and e-mail addresses for use in
various languages.

Exploitation and Public Announcements
=====================================

The Cisco PSIRT is not aware of any public announcements or malicious
use of the vulnerability described in this advisory.

Some of these vulnerabilities where reported to Cisco by customers that
experienced these issues during normal operation of their equipment.
The other vulnerabilities were discovered during internal testing.

Status of this Notice: FINAL
============================

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY
KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE
INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT
YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS
DOCUMENT AT ANY TIME.

A stand-alone copy or Paraphrase of the text of this document that
omits the distribution URL in the following section is an uncontrolled
copy, and may lack important information or contain factual errors.

Distribution
============

This advisory is posted on Cisco's worldwide website at :

http://www.cisco.com/warp/public/707/cisco-sa-20070214-fwsm.shtml

In addition to worldwide web posting, a text version of this notice is
clear-signed with the Cisco PSIRT PGP key and is posted to the
following e-mail and Usenet news recipients.

  * cust-security-announce@cisco.com
  * first-teams@first.org
  * bugtraq@securityfocus.com
  * vulnwatch@vulnwatch.org
  * cisco@spot.colorado.edu
  * cisco-nsp@puck.nether.net
  * full-disclosure@lists.grok.org.uk
  * comp.dcom.sys.cisco@newsgate.cisco.com

Future updates of this advisory, if any, will be placed on Cisco's
worldwide website, but may or may not be actively announced on mailing
lists or newsgroups. Users concerned about this problem are encouraged
to check the above URL for any updates.

Revision History
================

+-------------------------------------------------------------+
| Revision 1.0   | 2007-Feb-14   | Initial public release     |
+-------------------------------------------------------------+

Cisco Security Procedures
=========================

Complete information on reporting security vulnerabilities
in Cisco products, obtaining assistance with security
incidents, and registering to receive security information
from Cisco, is available on Cisco's worldwide website at
http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html.
This includes instructions for press inquiries regarding
Cisco security notices. All Cisco security advisories are available at
http://www.cisco.com/go/psirt.

- -----------------------------------------------------------------------
All contents are Copyright 1992-2007 Cisco Systems, Inc. All rights
reserved. 
- -----------------------------------------------------------------------

Updated: Feb 14, 2007                                Document ID: 72327

- -----------------------------------------------------------------------
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