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Vulnerability Note VU#635811Sun Solaris cachefsd vulnerable to heap overflow in cfsd_calloc() function via long string of charactersOverviewSun's NFS/RPC cachefs daemon (cachefsd) is shipped and installed by default with Sun Solaris 2.5.1, 2.6, 7, and 8 (SPARC and Intel architectures). Cachefsd caches requests for operations on remote file systems mounted via the use of NFS protocol. A remotely exploitable heap overflow exists in cachefsd that could permit a remote attacker to execute arbitrary code with the privileges of the cachefsd, typically root.I. DescriptionA remotely exploitable heap overflow exists in the cachefsd program shipped and installed by default with Sun Solaris 2.5.1, 2.6, 7, and 8 (SPARC and Intel architectures). A remote attacker can send a crafted RPC request to the cachefsd program to remotely exploit the vulnerability.Logs of exploitation attempts may resemble the following:
May 16 22:46:21 victim-host last message repeated 7 times May 16 22:46:22 victim-host inetd[600]: /usr/lib/fs/cachefs/cachefsd: Bus Error - core dumped May 16 22:46:24 victim-host inetd[600]: /usr/lib/fs/cachefs/cachefsd: Segmentation Fault - core dumped May 16 22:46:56 victim-host inetd[600]: /usr/lib/fs/cachefs/cachefsd: Bus Error - core dumped May 16 22:46:59 victim-host last message repeated 1 time May 16 22:47:02 victim-host inetd[600]: /usr/lib/fs/cachefs/cachefsd: Segmentation Fault - core dumped May 16 22:47:07 victim-host last message repeated 3 times May 16 22:47:09 victim-host inetd[600]: /usr/lib/fs/cachefs/cachefsd: Hangup May 16 22:47:11 victim-host inetd[600]: /usr/lib/fs/cachefs/cachefsd: Segmentation Fault - core dumped Sun Microsystems has released a Sun Alert Notification which addresses this issue as well as the issue described in VU#161931. According to the Sun Alert Notification, failed attempts to exploit this vulnerability will leave core dumps in the root directory. The presence of the core file does not preclude the success of subsequent attacks. Additionally, if the file /etc/cachefstab exists, it may contain unusual entries. This issue is also being referenced as CAN-2002-0033: II. ImpactA remote attacker can execute code with the privileges of the cachefsd process, typically root.III. SolutionThe CERT/CC is currently unaware of patches for this problem.According to a Sun Alert Notification a workaround is as follows:
#100235/1 tli rpc/tcp wait root /usr/lib/fs/cachefs/cachefsd cachefsd Once the line is commented out either: - reboot, or - send a HUP signal to inetd(1M) and kill existing cachefsd processes, for example, on Solaris 2.5.1 and 2.6 do the following: $ kill -HUP <PID of inetd> $ kill <PIDs of any cachefsd processes> Solaris 7 and 8 do the following: $ pkill -HUP inetd $ pkill cachefsd The possible side effects of the workaround are: - for systems not using cachefs: There is no impact. - for systems using cachefs: Only a "disconnected" operation is known to be affected by disabling cachefsd. This feature is rarely used outside of AutoClient. Mounts and unmounts should still succeed though an error message may be seen, "mount -F cachefs: cachefsd is not running". There is no performance impact. - for systems using AutoClient: The impact is unknown. Again, only "disconnected" mode is likely to be affected. Systems Affected
References
The CERT/CC acknowledges the Last Stage of Delirium Team for discovering and reporting on this vulnerability and thanks Sun Microsystems for their technical assistance. This document was written by Jason Rafail and Jeffrey Havrilla.
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