This advisory also applies to the corresponding versions of Kubuntu, Edubuntu, and Xubuntu.
Details follow:
It was discovered that bzip2 did not correctly handle certain malformed archives. If a user or automated system were tricked into processing a specially crafted bzip2 archive, applications linked against libbz2 could be made to crash, possibly leading to a denial of service.
Solution: The problem can be corrected by upgrading your system to the following package versions:
Ubuntu 6.06 LTS: libbz2-1.0 1.0.3-0ubuntu2.1
Ubuntu 6.10: libbz2-1.0 1.0.3-3ubuntu0.1
Ubuntu 7.04: libbz2-1.0 1.0.3-6ubuntu0.1
Ubuntu 7.10: libbz2-1.0 1.0.4-0ubuntu2.1
In general, a standard system upgrade is sufficient to effect the necessary changes.