Ubuntu Security Notice 948-1 – It was discovered that GnuTLS did not always properly verify the hash algorithm of X.509 certificates. If an application linked against GnuTLS processed a crafted certificate, an attacker could make GnuTLS dereference a NULL pointer and cause a DoS via application crash.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/90289/USN-948-1.txt
Source: https://packetstormsecurity.com/files/90289/Ubuntu-Security-Notice-948-1.html