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TUCoPS :: Linux :: Apps A-M :: n-032.txt

Double Free Bug in CVS Server (CIAC N-032)


                       The U.S. Department of Energy
                   Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___

                             INFORMATION BULLETIN

           Double-Free Bug in Concurrent Versions System (CVS) Server
                          [CERTŪ Advisory CA-2003-02]

January 23, 2003 19:00 GMT                                        Number N-032
PROBLEM:       Concurrent Versions System (CVS) is a version control and
               collaboration system that is widely used by open-source
               software development projects. A "double-free" vulnerability in
               the CVS server has been discovered allowing the potential for
               remote attacks.
AFFECTED       CVS prior to 1.11.5
DAMAGE:        A remote attacker could potentially leverage a heap corruption
               to gain root privileges and execute arbitrary code, alter
               program operation, read sensitive information, or cause a
               denial of service.
SOLUTION:      Apply the appropriate patch as specified by your vendor, or
               upgrade to CVS v1.11.5.
VULNERABILITY  The risk is HIGH. A remote attacker who is able to compromise a
ASSESSMENT:    CVS server could also potentially modify source-code
               repositories to contain Trojan horses, backdoors, or other
               malicious code.
 PATCHES:            Monitor CERT's bulletin for vendor updates and patches.
[***** Start CERTŪ Advisory CA-2003-02 *****]

CERTŪ Advisory CA-2003-02 Double-Free Bug in
CVS Server

Original issue date: January 22, 2003
Last revised: --
Source: CERT/CC

A complete revision history is at the end of this file. 

Systems Affected

Systems running CVS Home project versions of CVS prior to 1.11.5 
Operating system distributions that provide CVS 
Source code repositories managed by CVS 
For detailed vendor status information, see VU#650937 


A "double-free" vulnerability in the Concurrent Versions System (CVS) 
server could allow an unauthenticated, remote attacker with read-only 
access to execute arbitrary code, alter program operation, read sensitive 
information, or cause a denial of service. 

I. Description

CVS is a version control and collaboration system that is widely used by 
open-source software development projects. CVS is commonly configured to 
allow public, anonymous, read-only access via the Internet. 

The CVS server component contains a "double-free" vulnerability that can 
be triggered by a set of specially crafted directory requests. While 
processing these requests, an error-checking routine may attempt to free() 
the same memory reference more than once. Deallocating the already freed 
memory leads to heap corruption, which an attacker could leverage to 
execute arbitrary code, alter the logical operation of the CVS server 
program, or read sensitive information stored in memory. In most cases, 
heap corruption will result in a segmentation fault, causing a denial 
of service. 

The CVS server process is typically started by the Internet services 
daemon (inetd) and runs with root privileges. Arbitrary code inserted 
by an attacker would therefore run with root privileges. 

This issue is being tracked as VU#650937. This reference number 
corresponds to CVE candidate CAN-2002-0059. This issue was researched 
and reported by Stefan Esser of e-matters. 

II. Impact

Depending on configuration, operating system, and platform architecture, 
a remote attacker with anonymous, read-only access to a vulnerable CVS 
server could execute arbitrary code, alter the operation of the server 
program, read sensitive information, or cause a denial of service. 
There is also a significant secondary impact. An attacker who is able 
to compromise a CVS server could modify source-code repositories to 
contain Trojan horses, backdoors, or other malicious code. 

III. Solution

Apply a patch or upgrade

Apply the appropriate patch or upgrade as specified by your vendor. 
See Appendix A. below and the Systems Affected section of VU#650937 
for further information. 

Disable or restrict anonymous CVS access

As a temporary solution until patches or upgrades can be applied, 
or to improve the security of CVS servers in the long term,
consider the following workarounds and configurations: 

Disable anonymous CVS server access completely. 
Block or restrict access to CVS servers from untrusted hosts and 
networks. Anonymous access to CVS servers using :cvspserver: is 
typically provided on port 2401/tcp. 
Configure CVS servers to run in restricted (chroot) environments. 
Host CVS servers on single-purpose, secured systems. 

These workarounds and configurations are not complete solutions and 
will not prevent exploitation of this vulnerability. Other features
inherent in CVS may give anonymous users the ability to gain shell 

Appendix A. Vendor Information

This appendix contains information provided by vendors. When vendors 
report new information, this section is updated and the changes are 
noted in the revision history. If a vendor is not listed below, we 
have not received their comments. The Systems Affected section of 
VU#650937 contains additional vendor status information. 


Conectiva Linux is affected by this issue and updated packages are 
available at


An official announcement is pending and will show up in our updates 
website at shortly. 

Cray Inc.

Cray Inc. supports CVS through their Cray Open Software (COS) package. 
COS 3.3 and earlier is vulnerable. A new CVS will be available shortly. 
Please contact your local Cray service representative if you need this 
new package. 

CVS Home

CVS release 1.11.5 addresses this issue for CVS servers. CVS clients 
are not affected. 


Debian has updated their distribution with DSA 233. 

For the stable distribution (woody) this problem has been fixed in 
version 1.11.1p1debian-8.1. 

For the old stable distribution (potato) this problem has been 
fixed in version 1.10.7-9.2. 

For the unstable distribution (sid) this problem will be fixed soon. 


SOURCE: Hewlett-Packard Company and Compaq Computer Corporation, 
a wholly-owned subsidiary of Hewlett-Packard Company

                      RE: x-reference SSRT3463

                      Not Vulnerable:
                      HP Tru64 UNIX
                      HP NonStop Servers
                      HP OpenVMS

To report any security issue for any HP software products send email 


The AIX operating system does not ship with CVS. However, CVS is 
available for installation on AIX from the Linux Affinity Toolbox. 

CVS versions 1.11.1p1-2 and earlier are vulnerable to the issues 
discussed in CERT Vulnerability Note VU#650937 and any advisories 
which follow. 

Users are advised to download CVS 1.11.1p1-3 from:

Please note that the above address was wrapped to two lines. 

CVS 1.11.1p1-3 contains the security fixes made in CVS 1.11.5 to 
address these issues. 

This software is offered on an "as-is" basis. 

Openwall GNU/*/Linux

We don't yet re-distribute CVS in Openwall GNU/*/Linux. We do, 
however, provide public anonymous CVS access to a copy of our 
repository, hosted off a separate machine and in a chroot jail. 
This kind of vulnerabilities in CVS was expected, and our 
anoncvs setup is mostly resistant to them: read-only access to 
the repository is achieved primarily with the use of regular 
Unix permissions, not controls built into CVS. CVS LockDir option 
is used to direct CVS lock files to a separate directory tree, 
actually writable to the pseudo-user. Nevertheless, the anoncvs 
server has been upgraded to CVS 1.11.5 a few hours after it 
was released. 

Red Hat, Inc.

Red Hat Linux and Red Hat Linux Advanced Server shipped with a 
cvs package vulnerable to these issues. New cvs packages are 
now available along with our advisory at the URLs below. Users 
of the Red Hat Network can update their systems using the 
'up2date' tool. 

Red Hat Linux Advanced Server: 

Red Hat Linux: 

Sun Microsystems Inc.

Sun does not include CVS with Solaris and therefore Solaris is 
not affected by this issue. 

Sun Linux, versions 5.0.3 and below, does ship with a vulnerable 
CVS package. Sun recommends that CVS services be disabled on 
affected Sun Linux systems until patches are available for 
this issue. 

Sun will be publishing a Sun Alert for Sun Linux describing the 
patch information which will be available from: 


Appendix B. References

CERT/CC Vulnerability Note VU#650937 
e-matters Advisory 01/2003 

This vulnerability was reported by Stefan Esser of e-matters. 

Author: Art Manion. 

This document is available from: 

CERT/CC Contact Information

Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
Postal address:
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890

CERT/CC personnel answer the hotline 08:00-17:00 EST(GMT-5) / EDT(GMT-4) 
Monday through Friday; 
they are on call for emergencies during other hours, on U.S. holidays, 
and on weekends. 

Using encryption

We strongly urge you to encrypt sensitive information sent by email. 
Our public PGP key is available from 

If you prefer to use DES, please call the CERT hotline for more 

Getting security information

CERT publications and other security information are available 
from our web site 

To subscribe to the CERT mailing list for advisories and bulletins, 
send email to Please include in the body of
your message

                 subscribe cert-advisory 

* "CERT" and "CERT Coordination Center" are registered in the U.S. 
Patent and Trademark Office. 

Any material furnished by Carnegie Mellon University and the Software 
Engineering Institute is furnished on an "as is" basis. Carnegie Mellon 
University makes no warranties of any kind, either expressed or implied 
as to any matter including, but not limited to, warranty of fitness for 
a particular purpose or merchantability, exclusivity or results obtained
from use of the material. Carnegie Mellon University does not make any 
warranty of any kind with respect to freedom from patent, trademark, 
or copyright infringement. 

Conditions for use, disclaimers, and sponsorship information 

Copyright 2003 Carnegie Mellon University.

Revision History 

January 22, 2003: Initial release

[***** End CERTŪ Advisory CA-2003-02 *****]

CIAC wishes to acknowledge the contributions of CERT for the
information contained in this bulletin.

CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
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