USN-636-1: Postfix vulnerability

Referenced CVEs: CVE-2008-2936Description: 
Ubuntu Security Notice USN-636-1 August 19, 2008
postfix vulnerability

A security issue affects the following Ubuntu releases:

Ubuntu 6.06 LTS
Ubuntu 7.04
Ubuntu 7.10
Ubuntu 8.04 LTS

This advisory also applies to the corresponding versions of
Kubuntu, Edubuntu, and Xubuntu.

The problem can be corrected by upgrading your system to the
following package versions:

Ubuntu 6.06 LTS:
postfix 2.2.10-1ubuntu0.2

Ubuntu 7.04:
postfix 2.3.8-2ubuntu0.2

Ubuntu 7.10:
postfix 2.4.5-3ubuntu1.2

Ubuntu 8.04 LTS:
postfix 2.5.1-2ubuntu1.1

In general, a standard system upgrade is sufficient to effect the
necessary changes.

Details follow:

Sebastian Krahmer discovered that Postfix was not correctly handling
mailbox ownership when dealing with Linux's implementation of hardlinking
to symlinks. In certain mail spool configurations, a local attacker
could exploit this to append data to arbitrary files as the root user.
The default Ubuntu configuration was not vulnerable.