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PuTTY SSH2 Client Software Access Control Bug May Disclose Passwords to Local Users Via Memory
SecurityTracker Alert ID: 1006014|
SecurityTracker URL: http://securitytracker.com/id/1006014
(Links to External Site)
Updated: Jun 13 2008|
Original Entry Date: Jan 29 2003
Disclosure of authentication information|
Fix Available: Yes Vendor Confirmed: Yes Exploit Included: Yes |
A vulnerability was reported in the PuTTY SSH2 client software. A local user may be able to obtain the target user's password from memory. Other vendor implementations are also affected.|
iDEFENSE reported that the client does not properly remove the user's password from memory after authentication. A local user with access to memory or to a memory dump can retrieve the target user's password.
According to the report, the password can be found in memory following the second occurrence of the string "password:".
A local user with access to system memory can obtain the client user's password.|
The current development snapshots of PuTTY are reported to be fixed. They are available via CVS at:|
Vendor URL: www.chiark.greenend.org.uk/~sgtatham/putty/ (Links to External Site)
Access control error|
Source Message Contents
Date: Wed, 29 Jan 2003 12:51:42 -0500|
Subject: iDEFENSE Security Advisory 01.28.03: SSH2 Clients Insecurely Store Passwords
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iDEFENSE Security Advisory 01.28.03: SSH2 Clients Insecurely Store
Passwords (AbsoluteTelnet, SecureCRT, Entunnel, SecureFx, and PuTTY)
January 28, 2003
PuTTY is a free implementation of Telnet and SSH for Win32 platforms,
along with an xterm terminal emulator. More information is available at
SecureCRT provides security for remote access, file transfer, and data
tunneling by combining the open Secure Shell protocol with emulation.
Entunnel provides SSH2 data tunneling (port forwarding) services when
connected to an SSH2 server. The SecureFX client application is an SFTP
and FTP over an encrypted SSH2 client. More information is available at
AbsoluteTelnet is a terminal client program developed for the Microsoft
Windows platform. AbsoluteTelnet supports multiple protocols including
Telnet, SSH1, SSH2, TAPI Dialup and direct COM. More information is
available at http://www.celestialsoftware.net/telnet/index.html.
AbsoluteTelnet, SecureCRT, Entunnel, SecureFx, and PuTTY do not properly
scrub memory allowing an attacker with access to memory or a memory dump
to retrieve authentication information.
When connected via SSH2, an attacker can search memory or a memory dump
for logon credentials. Passwords transmitted by PuTTY can be found by
searching for the second occurrence of the string "password:". The user's
password is stored in plaintext shortly after this string. Passwords
transmitted by SecureCRT can be found by searching for the string
"ssh-connection". The logon and password is stored in plaintext on the
respective sides of this keyword. Passwords transmitted by AbsoluteTelnet
can be found by searching for the first occurrence of the string
"Password", that lies in a segment of read/write memory. The logon and
password is stored in plaintext on the respective sides of this keyword.
An attacker able to ascertain a target user's memory dump will be able to
recover passwords for remote systems. This is of special concern in shared
iDEFENSE has verified the existence of this vulnerability in the following
versions of the above mentioned clients:
• AbsoluteTelnet: latest (2.11)
• SecureCRT: latest (4.0.2) and 3.4.6
• SecureFX : 2.1.2 and 2.0.4
• Entunnel: 1.0.2 and earlier
• PuTTY: latest (0.53b)
Earlier versions of the tested clients as well as other clients may be
vulnerable as well.
V. VENDOR RESPONSE(S)/FIX
Current development snapshots of PuTTY are believed to have this problem
fixed. Unfortunately, we are in the middle of heavy code restructuring and
not currently in a position to make a stable release, but the current
snapshots should be good enough for anyone for whom this is a problem.
The SSH password vulnerability discovered by iDEFENSE has been found to
exist in all versions of AbsoluteTelnet prior to (and including) version
Version 2.12, which Celestial Software will make available as a FREE
update to ALL existing users, fixes the problem by keeping password memory
"scrubbed" and free of plaintext copies of the password.
Version 2.12 is currently in beta testing pending the beta test group's
acceptance of the changes it contains. Upon release, it will be available
for download at the Celestial Software website:
For a sneak peak at the 2.12 beta, go here:
Thanks to iDEFENSE for bringing this to my attention and for allowing
adequate time to make corrections! In particular, thanks to David Endler
for staying on top of this!
VanDyke Software recognizes the efforts of iDEFENSE in discovering this
security issue and commends iDEFENSE for the responsible manner in which
the security issue was made known so as to allow time for revisions to be
made before the information was released to the public.
The vulnerability reported by iDEFENSE exists in the following versions of
VanDyke Software client applications:
SecureCRT: 4.0.2 and 3.4.7
SecureFX : 2.1.2 and 2.0.4
Entunnel: 1.0.2 and earlier
Earlier versions of these client applications are vulnerable as well.
VanDyke encourages all users whose licenses were purchased prior to June
1, 2000 to consider upgrading to the current version(s) of their licensed
Vulnerability fix downloads are available:
SecureCRT 4.0.3 - http://www.vandyke.com/download/securecrt/index.html
SecureCRT 3.4.8 -
SecureFX 2.1.3 - http://www.vandyke.com/download/securefx/index.html
SecureFX 2.0.5 -
Entunnel 1.0.3 - http://www.vandyke.com/download/entunnel/index.html
VI. CVE INFORMATION
The Mitre Corp.'s Common Vulnerabilities and Exposures (CVE) Project
assigned the following identification numbers to these issue:
CAN-2003-0046 - AbsoluteTelnet
CAN-2003-0047 - SecureCRT
CAN-2003-0048 - PuTTY, SecureFx, and Entunnel
VII. DISCLOSURE TIMELINE
12/13/2002 Issues disclosed to iDEFENSE
01/09/2003 firstname.lastname@example.org, Mark.Walker@vandyke.com, and
01/09/2003 iDEFENSE clients notified
01/09/2003 Response received from Simon Tatham [email@example.com]
01/10/2003 Response received from Celestial Software
01/10/2003 Response received from Van Dyke Software
01/28/2003 Coordinated public disclosure
Knud Erik Højgaard (firstname.lastname@example.org) discovered these vulnerabilities.
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vulnerabilities and hacker profiling to the global spread of viruses
and other malicious code. Our security intelligence services provide
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visit http://www.idefense.com .
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