The remote host is missing an update to gnupg2 announced via advisory USN-970-1.
Details follow:
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.
Solution: The problem can be corrected by upgrading your system to the following package versions:
Ubuntu 8.04 LTS: gpgsm 2.0.7-1ubuntu0.1
Ubuntu 9.04: gpgsm 2.0.9-3.1ubuntu0.1
Ubuntu 9.10: gpgsm 2.0.12-0ubuntu2.1
Ubuntu 10.04 LTS: gpgsm 2.0.14-1ubuntu1.2
In general, a standard system update will make all the necessary changes.