Ubuntu Security Notice USN-809-1 – Multiple vulnerabilities in gnutls12, gnutls13, and gnutls26 have been addressed.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/80510/USN-809-1.txt
Source: https://packetstormsecurity.com/files/80510/Ubuntu-Security-Notice-809-1.html