The remote host is missing an update to thunderbird announced via advisory USN-817-1.

The problem can be corrected by upgrading your system to the following package versions: Ubuntu 8.04 LTS: thunderbird 2.0.0.23+build1+nobinonly-0ubuntu0.8.04.1 Ubuntu 8.10: thunderbird 2.0.0.23+build1+nobinonly-0ubuntu0.8.10.1 Ubuntu 9.04: thunderbird 2.0.0.23+build1+nobinonly-0ubuntu0.9.04.1 After a standard system upgrade you need to restart Thunderbird to effect the necessary changes. https://secure1.securityspace.com/smysecure/catid.html?in=USN-817-1 http://launchpad.net/bugs/416646

Several flaws were discovered in the rendering engine of Thunderbird. If Javascript were enabled, an attacker could exploit these flaws to crash Thunderbird.