Several security issues were fixed in GnuPG.
Daniel Kahn Gillmor discovered that GnuPG treated keys with empty usage flags as being valid for all usages. (CVE-2013-4351)
9 October 2013
A security issue affects these releases of Ubuntu and its derivatives:
Several security issues were fixed in GnuPG.
Daniel Kahn Gillmor discovered that GnuPG treated keys with empty usage flags as being valid for all usages. (CVE-2013-4351)
Taylor R Campbell discovered that GnuPG incorrectly handled certain OpenPGP messages. If a user or automated system were tricked into processing a specially-crafted message, GnuPG could consume resources, resulting in a denial of service. (CVE-2013-4402)
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.