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

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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:

     <http://www.kb.cert.org/vuls/id/650937#systems>

Overview

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.

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

 <http://www.kb.cert.org/vuls/id/650937>

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

 <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2003-0015>

This issue was researched and reported by Stefan Esser of
e-matters:

 <http://security.e-matters.de/advisories/012003.html>

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:

 <http://www.kb.cert.org/vuls/id/650937#systems>

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
access.

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:

<http://www.kb.cert.org/vuls/id/650937#systems>

Conectiva

 Conectiva  Linux is affected by this issue and updated packages are
 available at <ftp://atualizacoes.conectiva.com.br/>:
 
 6.0/SRPMS/cvs-1.10.8-5U60_3cl.src.rpm
 6.0/RPMS/cvs-1.10.8-5U60_3cl.i386.rpm
 6.0/RPMS/cvs-doc-1.10.8-5U60_3cl.i386.rpm
 7.0/SRPMS/cvs-1.11-7U70_2cl.src.rpm
 7.0/RPMS/cvs-1.11-7U70_2cl.i386.rpm
 7.0/RPMS/cvs-doc-1.11-7U70_2cl.i386.rpm
 8/SRPMS/cvs-1.11-9U80_2cl.i386.rpm
 8/RPMS/cvs-1.11-9U80_2cl.i386.rpm
 8/RPMS/cvs-doc-1.11-9U80_2cl.i386.rpm
 
 An official announcement is pending and will show up in our updates
 website at  <http://distro.conectiva.com.br/atualizacoes?idioma=en>
 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

 Debian has updated their distribution with DSA 233.
 <http://www.debian.org/security/2003/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.

Hewlett-Packard

 SOURCE:  Hewlett-Packard Company and Compaq Computer Corporation, a
 wholly-owned subsidiary of Hewlett-Packard Company
 
 RE: x-reference SSRT3463
 
 Not Vulnerable:
 
 HP-UX
 HP-MPE/ix
 HP Tru64 UNIX
 HP NonStop Servers
 HP OpenVMS
 
 To  report  any  security  issue  for any HP software products send
 email to <[email protected]>

IBM

 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:

 <ftp://ftp.software.ibm.com/aix/freeSoftware/aixtoolbox/RPMS/ppc/
 cvs/cvs-1.11.1p1-3.aix4.3.ppc.rpm>
 
 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:

 <http://rhn.redhat.com/errata/RHSA-2003-013.html>

 Red Hat Linux:

 <http://rhn.redhat.com/errata/RHSA-2003-013.html>

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:

 <http://sunsolve.Sun.COM>

Appendix B. References

 * CERT/CC Vulnerability Note VU#650937 -
   <http://www.kb.cert.org/vuls/id/650937>
 * e-matters Advisory 01/2003 -
   <http://security.e-matters.de/advisories/012003.html>

 _________________________________________________________________

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

Author: Art Manion.

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This document is available from:
<http://www.cert.org/advisories/CA-2003-02.html&gt;

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Revision History

January 22, 2003: Initial release

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