Clam AntiVirus 'clamav-milter' Format String Flaw Lets Remote Users Execute Arbitrary Code
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SecurityTracker Alert ID: 1008157
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CVE Reference: CAN-2003-0946
(Links to External Site)
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Updated: Nov 19 2003
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Original Entry Date: Nov 12 2003
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Impact: Denial of service via network, Execution of arbitrary code via network, Root access via network, User access via network
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Fix Available: Yes
Vendor Confirmed: Yes
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Advisory: Strategic Reconnaissance Team
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Version(s): confirmed on 0.60 - 0.60p
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Description: A format string vulnerability was reported in Clam AntiVirus. A remote user can execute arbitrary code on the target system.
Secure Network Operations Strategic Reconnaissance Team reported that clamav-milter contains a format string flaw that can be exploited
by a remote user if syslog support is configured.
A remote user can send an e-mail with a specially crafted "From:" address containing
"%" characters and with e-mail content that will trigger a virus rule to the target system. In this case, the remote user's e-mail
address will be passed to syslog() without appropriate validation. The syslog call is reportedly made without a format specifier.
A remote user can cause the target Clam AntiVirus software to crash or to execute arbitrary code.
A demonstration exploit string
is provided:
"mail from: %n%n%n%n%n%n%n"
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Impact: A remote user can cause the 'clamav-milter' process to crash or execute arbitrary code. The arbitrary code will run with the privileges of the Clam AntiVirus user or with root privileges, depending on how the system is configured.
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Solution: The vendor has released a fix in clamav-devel-20031111 and clamav-0.65, available at:
http://cvs.sourceforge.net/viewcvs.py/clamav/clamav-devel/
http://prdownloads.sou
rceforge.net/clamav/
The author of the report indicates that you can, as a workaround, disable syslog support.
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Vendor URL: clamav.elektrapro.com/ (Links to External Site)
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Cause: Input validation error
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Underlying OS: Linux (Any), UNIX (Any)
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Reported By: KF <dotslash@snosoft.com>
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Message History:
None.
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Source Message Contents
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Date: Wed, 12 Nov 2003 15:07:19 -0500
From: KF <dotslash@snosoft.com>
Subject: SRT2003-11-11-1151 - clamav-milter remote exploit / DoS
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Secure Network Operations, Inc. http://www.secnetops.com/research
Strategic Reconnaissance Team research@secnetops.com
Team Lead Contact kf@secnetops.com
Our Mission:
************************************************************************
Secure Network Operations offers expertise in Networking, Intrusion
Detection Systems (IDS), Software Security Validation, and
Corporate/Private Network Security. Our mission is to facilitate a
secure and reliable Internet and inter-enterprise communications
infrastructure through the products and services we offer.
To learn more about our company, products and services or to request a
demo of ANVIL FCS please visit our site at http://www.secnetops.com, or
call us at: 978-263-3829
Quick Summary:
************************************************************************
Advisory Number : SRT2003-11-11-1151
Product : Clam AntiVirus
Version : clamav-0.60 through clamav-0.60p
Vendor : http://clamav.elektrapro.com/
Class : Remote
Criticality : High (to clamav-milter users)
Operating System(s) : *nix, cygwin
Notice
************************************************************************
The full technical details of this vulnerability can be found at:
http://www.secnetops.com under the research section.
Basic Explanation
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High Level Description : clamav-milter contains format strings issues.
What to do : disable syslog support, upgrade to clamav-0.65
Basic Technical Details
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Proof Of Concept Status : SNO has proof of concept.
Low Level Description : Clam AntiVirus is an anti-virus toolkit for
UNIX. The main purpose of the software is to integrate with mail servers
for attachment scanning. Clam AntiVirus works with Linux, Solaris,
FreeBSD, OpenBSD, NetBSD, AIX, Mac OS X, and Cygwin B20.
Snapshot clamav-devel-20031111 and clamav-0.65 fix a potentially
exploitable format string issue that can be triggered by a remote attacker.
Only versions above clamav-0.54 that include syslog() functionality are
vulnerable to this attack. CVS snapshots up to but not including version
clamav-devel-20031111 may be vulnerable to attack. Versions clamav-0.60
through clamav-0.60p are confirmed to be at least exploitable for a DoS
condition. This issue only poses a problem for clamav-milter users.
* 0.60q 11/11/03 Fixed handling of % characters in e-mail addresses
* pointed out by dotslash@snosoft.com
This issue may potentially be used to run code as either the clamav user or
root depending on how clamav is configured. At the very least a DoS attack
on clamav-milter can be caused using "mail from: %n%n%n%n%n%n%n" along with
a test antivirus string which is used to trigger an AV alert.
full details at http://www.secnetopz.biz/research/SRT2003-11-11-1151.txt
Vendor Status : Promptly attended to the issue. Patched
clamav-milter is available in clamav-devel-20031111 and clamav-0.65
Bugtraq URL : To be assigned.
Disclaimer
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This advisory was released by Secure Network Operations,Inc. as a matter
of notification to help administrators protect their networks against
the described vulnerability. Exploit source code is no longer released
in our advisories but can be obtained under contract.. Contact our sales
department at sales@secnetops.com for further information on how to
obtain proof of concept code.
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Secure Network Operations, Inc. || http://www.secnetops.com
"Embracing the future of technology, protecting you."
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