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Vulnerability Note VU#650937
Concurrent Versions System (CVS) server improperly deallocates memory
OverviewA "double-free" vulnerability in the Concurrent Versions System (CVS) server could allow a remote attacker to execute arbitrary code or commands or cause a denial of service on a vulnerable system.
I. DescriptionCVS is a source code maintenance system that is widely used by open-source software development projects.
The CVS server component contains a "double-free" vulnerability that can be triggered by a set of specially crafted directory change 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 can lead to heap corruption, which may be leveraged by an attacker to execute arbitrary code. The CVS server process is commonly started by the Internet services daemon (inetd) and run with root privileges.
CVS clients are not affected.
II. ImpactDepending on configuration, operating system, and platform architecture, a remote attacker with anonymous read-only access to a vulnerable CVS server could execute arbitrary code, read sensitive information, or cause a denial of service. There is a significant secondary impact in that source code maintained in CVS repositories could be modified to include trojan horses, backdoors, or other malicious code.
III. Solution
Patch or Upgrade
Apply the appropriate patch or upgrade as specified by your vendor. This vulnerability is resolved in CVS 1.11.5.
Disable CVS Server
Until patches are available and can be applied, consider disabling the CVS server.
Disable Anonymous CVS Access
Disable anonymous access to the CVS server.
Block or Restrict Access
Block or restrict access to the CVS server from untrusted hosts and networks. The CVS server typically listens on 2401/tcp, but may use another port or protocol.
Limit CVS Server Privileges
- Configure CVS server to run in a restricted (chroot) environment.
- Run CVS servers with the minimum set of privileges required on the host file system.
- Provide separate systems for development (write) and public/anonymous (read-only) CVS access.
- Host public/anonymous CVS servers on single-purpose, secured systems.
Note that none of these workarounds will prevent exploitation of this vulnerability. These workarounds will only limit the scope and impact of possible attacks. Other features inherent in CVS may give anonymous users the ability to gain shell access.
Systems Affected
References
http://security.e-matters.de/advisories/012003.html
http://ccvs.cvshome.org/servlets/NewsItemView?newsID=51
http://www.cvshome.org/docs/manual/cvs_1.html
http://www.netsys.com/library/papers/chrooted-ssh-cvs-server.txt
http://openbsd.sunsite.ualberta.ca/papers/anoncvs-paper.ps
Credit
This vulnerability was publicly reported by Stefan Esser of e-matters.
This document was written by Art Manion.
Other Information
| Date Public | 01/20/2003 |
| Date First Published | 01/21/2003 11:34:25 AM |
| Date Last Updated | 08/20/2003 |
| CERT Advisory | CA-2003-02 |
| CVE Name | CAN-2003-0015 |
| US-CERT Technical Alerts | |
| Metric | 40.10 |
| Document Revision | 33 |
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