It was discovered that GPGSM in GnuPG2 did not correctly handle certificates with a large number of Subject Alternate Names. If a user or automated system were tricked into processing a specially crafted certificate, an attacker could cause a denial of service or execute arbitrary code with privileges of the user invoking the program.
The problem can be corrected by updating your system to the following package versions:
11 August 2010
A security issue affects these releases of Ubuntu and its derivatives:
It was discovered that GPGSM in GnuPG2 did not correctly handle certificates with a large number of Subject Alternate Names. If a user or automated system were tricked into processing a specially crafted certificate, an attacker could cause a denial of service or execute arbitrary code with privileges of the user invoking the program.
The problem can be corrected by updating your system to the following package versions:
To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.
In general, a standard system update will make all the necessary changes.