Original release date: September 16, 2003
Last revised: Aug 12, 2008
A complete revision history can be found at the end of this file.
- Systems running versions of OpenSSH prior to 3.7.1
- Systems that use or derive code from vulnerable versions of OpenSSH
There is a remotely exploitable vulnerability in a general buffer management
function in versions of OpenSSH prior to 3.7.1. This may allow a remote
attacker to corrupt heap memory which could cause a denial-of-service
condition. It may also be possible for an attacker to execute arbitrary code.
We are updating this advisory to inform users that Version 3.7.1 of
OpenSSH has been released to patch a similar vulnerability in the buffer
There are two errors in the buffer management code of OpenSSH. These
vulnerabilities affect versions prior to 3.7.1. Version 3.7 is affected
by one of these errors. The errors occur when a buffer is allocated for a
large packet. When the buffer is cleared, an improperly sized chunk of
memory is filled with zeros. This leads to heap corruption, which could
cause a denial-of-service condition. These vulnerabilities may also allow
an attacker to execute arbitrary code.
The OpenSSH advisory has been updated to include a patch for version
3.7 as well as 3.6.1 and prior.
Other systems that use or derive code from OpenSSH may be affected. This
includes network equipment and embedded systems. We have monitored
incident reports that may be related to this vulnerability.
Vulnerability Note VU#333628
lists the vendors we contacted about these vulnerabilities. The
vulnerability note is available from
This vulnerability has been assigned the following Common Vulnerabilities
and Exposures (CVE) number:
While the full impact of this issues are unclear, the most
likely result is heap corruption, which could lead to a denial of
If it is possible for an attacker to execute arbitrary code, then they may be able to so with the
privileges of the user running the sshd process, typically root.
This impact may be limited on systems using the privilege separation
(privsep) feature available in OpenSSH.
Upgrade to OpenSSH version 3.7.1
This vulnerability is resolved in OpenSSH version 3.7.1, which is
available from the OpenSSH web site at
Apply a patch from your vendor
A patches for these issues are included in the OpenSSH advisory
This patch may be manually applied to correct this vulnerability in
affected versions of OpenSSH. If your vendor has provided a patch or
upgrade, you may want to apply it rather than using the patch from
OpenSSH. Find information about vendor patches in Appendix A. We will update this document as
vendors provide additional information.
Use privilege separation to minimize impact
System administrators running OpenSSH versions 3.2 or higher may be
able to reduce the impact of this vulnerability by enabling the
"UsePrivilegeSeparation" configuration option in their sshd
configuration file. Typically, this is accomplished by creating a
privsep user, setting up a restricted (chroot) environment, and adding
the following line to /etc/ssh/sshd_config:
This workaround does not prevent this vulnerability from
being exploited, however due to the privilege separation mechanism,
the intruder may be limited to a constrained chroot environment with
restricted privileges. This workaround will not prevent this
vulnerability from creating a denial-of-service condition. Not all
operating system vendors have implemented the privilege separation
code, and on some operating systems it may limit the functionality of
OpenSSH. System administrators are encouraged to carefully review the
implications of using the workaround in their environment and use a
more comprehensive solution if one is available. The use of privilege
separation to limit the impact of future vulnerabilities is
Appendix A. - Vendor Information
This appendix contains information provided by vendors for this advisory.
As vendors report new information to the CERT/CC, we will update this section
and note the changes in the revision history. Additional vendors who have not provided direct statements, but who have made
public statements or informed us of their status are listed in VU#333628. If a vendor is
not listed below or in VU#333628, we have not
received their comments.
AppGate Network Security AB
AppGate versions from 4.0 up to and including 5.3.1 does include the
vulnerable code. Patches are available from the appgate support pages at
Apple Computers Inc.
Mac OS X 10.2.8 contains the patches to address CVE
CAN-2003-0695, and CAN-2003-0682. On Mac OS X versions prior to 10.2.8,
the vulnerability is limited to a denial of service from the possibility
of causing sshd to crash. Each login session has its own sshd, so
established connections are preserved up to the point where system
resources are exhausted by an attack.
To deliver the update in a rapid and reliable manner, only the patches
for CVE IDs listed above were applied, and not the entire set of patches
for OpenSSH 3.7.1. Thus, the OpenSSH version in Mac OS X 10.2.8, as
obtained via the "ssh -V" command, is:
OpenSSH_3.4p1+CAN-2003-0693, SSH protocols 1.5/2.0, OpenSSL 0x0090609f
Mac OS X 10.2.8 is available as a free update for customers running
Mac OS X 10.2.x. It is available from:
Mac OS X Client (updating from 10.2 - 10.2.5):
Mac OS X Client (updating from 10.2.6 - 10.2.7):
Mac OS X Server (updating from 10.2 - 10.2.5):
Mac OS X Server (updating from 10.2.6 - 10.2.7):
Our software shares no codebase with the OpenSSH implementation, therefore we
believe that, in our products, this problem does not exist.
Cisco has some products which are vulnerable to this issue. Cisco's response
is now published at
Cray Inc. supports OpenSSH through its Cray Open Software (COS) package. Cray
is vulnerable to this buffer management error and is in the process of
compiling OpenSSH 3.7. The new version will be made available in the next COS
Debian has issued DSA 382 and DSA 383 for these issues.
This vulnerability does not affect any version of F-Secure
SSH software that utilizes ssh protocol version 2. The
non-affected versions have been available since 1998.
This vulnerability only affects the following F-Secure SSH
server versions: F-Secure SSH for Unix versions 1.3.14 and
More information is available from
The AIX Security Team is aware of the issues discussed
Vulnerability Note VU#333628 and CERT Advisory
OpenSSH is available for AIX via the AIX Toolbox for
Linux or the
OpenSSH 3.4p1, revision 9 contains fixes for this issue
for the AIX Toolbox
for Linux. For more information about the AIX Toolbox for
Linux or to download
OpenSSH 3.4p1 revision 9, please see:
Please note that AIX Toolbox for Linux is available
"as-is" and is unwarranted.
Patched versions of OpenSSH for the Bonus Pack on AIX 5.1
and 5.2 are available
Juniper Networks has identified this vulnerability in all
shipping versions of JUNOS and coded a software fix. The fix
will be included in all releases of JUNOS Internet software
built on or after September 17. Customers with current
support contracts should contact JTAC to obtain the fix for
JUNOSe and SDX are not vulnerable to this issue.
Contract customers can review the details at:
Mandrake Linux is affected and MDKSA-2003:090 will be released today with
patched versions of OpenSSH to resolve this issue.
Mirapoint released a patch (D3_SSH_CA_2003_24) last night to fix the first reported vulnerability and will release D3_SSH_CA_2003_24_1 to cover the
The NetBSD Security Advisory on the OpenSSH buffer management issue is available here:
This issue applies only to SecureAdmin on Data ONTAP versions earlier than 6.4.3, and SecureAdmin for NetCache releases earlier than 5.5R2.
All current releases (NetCache 5.6, 6.0 and 6.1, and Filer 6.5, 7.0, 7.1, 7.2, 7.3 and 10.0) have been secured against this issue.
If you have an affected release:
Disable the SSH server on the filer or NetCache appliance, or if it must remain enabled, ensure that the ssh.access option (config.admin.trusted_hosts in NetCache) is used to restrict ssh connections to authorized administrative hosts.
The OpenSSH package in Openwall GNU/*/Linux did contain the buffer /
memory management errors. As of 2003/09/17, we have included the fixes
from OpenSSH 3.7.1 as well as 4 additional fixes to other such real or
potential errors based on an exhaustive review of the OpenSSH source
code for uses of *realloc() functions. At this time, it is uncertain
whether and which of these bugs are exploitable. If exploits are
possible, due to privilege separation, the worst direct impact should
be limited to arbitrary code execution under the sshd pseudo-user
account restricted within the chroot jail /var/empty, or under the
logged in user account
We have tested our code and double checked for the code vulnerability and
we have found that our code is NOT vulnerable.
PuTTY is not based on the OpenSSH code base, so it should not be vulnerable to
any OpenSSH-specific attacks.
Red Hat, Inc.
Red Hat Linux and Red Hat Enterprise Linux ship with an
vulnerable to these issues. Updated OpenSSL packages are
along with our advisory at the URLs below. Users of the Red
Network can update their systems using the 'up2date' tool.
Red Hat Linux:
Red Hat Enterprise Linux:
Riverstone Networks has issued an advisory on this issue at http://www.riverstonenet.com/support/tb0265-9.html.
Secure Computing Corporation
Sidewinder(r) and Sidewinder G2 Firewall(tm) (including all appliances)
Sidewinder v5.x & Sidewinder G2 v6.x's embedded Type Enforcement(r)
technology strictly limits the capabilities of Secure Computing's modified
version of the OpenSSH daemon code integrated into the firewall's SecureOS
operating system. Any attempt to exploit this vulnerability in the
OpenSSH daemon code running on the firewalls results in an automatic
termination of the attacker's connection and multiple Type Enforcement
Gauntlet(tm) & e-ppliance
Gauntlet and e-ppliance do not include SSH server software, and are
thus immune to this vulnerability.
SSH Communications Security
SSH Secure Shell products do not contain the buffer
management error. SSH Communications Security products have
different code base than OpenSSH.
The Solaris Secure Shell in Solaris 9 is impacted by this issue described in CERT Vulnerability Note VU#333628. Sun has published Sun Alert 56861 available here:
which details the impact, contributing factors, workaround options, and resolution. This issue does not affect the Solaris Secure Shell in Solaris 10.
The CERT/CC thanks Markus Friedl of the OpenSSH project for his technical
assistance in producing this advisory.
A. Rafail and Art Manion
Copyright 2003 Carnegie Mellon University.
September 16, 2003: Initial release
September 17, 2003: Updated with new information regarding 3.7.1 release
September 17, 2003: Added SSH Communications Security vendor statement
September 17, 2003: Added Red Hat, Inc. vendor statement
September 17, 2003: Added Sun Microsystems vendor statement
September 17, 2003: Added NetBSD vendor statement
September 17, 2003: Added Network Appliance vendor statement
September 18, 2003: Added Cisco vendor statement
September 18, 2003: Updated Red Hat, Inc. links in vendor statement
September 18, 2003: Added IBM vendor statement
September 18, 2003: Added F-Secure vendor statement
September 18, 2003: Added OpenWall GNU/*/Linux vendor statement
September 22, 2003: Added Juniper Networks vendor statement
September 22, 2003: Added Mirapoint vendor statement
September 23, 2003: Added Secure Computing Corp. vendor statement
September 23, 2003: Added AppGate Network Security AB vendor statement
October 01, 2003: Added Apple Computers vendor statement
October 01, 2003: Added Pragma Systems vendor statement
October 01, 2003: Updated IBM vendor statement
October 01, 2003: Added Riverstone vendor statement
January 16, 2007: Updated Sun vendor statement
August 12, 2008: Updated Network Appliance vendor statement