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


CERT 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

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.

The CERT/CC is tracking this issue as VU#650937:


This reference number corresponds to CVE candidate CAN-2002-0059:


This issue was researched and reported by Stefan Esser of


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 <>

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


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

RE: x-reference SSRT3463

Not Vulnerable:

HP NonStop Servers

To report any security issue for any HP software products send
email to <>


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

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

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

Email: <>
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Fax: +1 412-268-6989
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Revision History

January 22, 2003: Initial release

Version: PGP 6.5.8


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