Ubuntu Security Notice USN-264-1 – Tavis Ormandy discovered a flaw in gnupg’s signature verification. In some cases, certain invalid signature formats could cause gpg to report a ‘good signature’ result for auxiliary unsigned data which was prepended or appended to the checked message part.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/44613/USN-264-1.txt
Source: https://packetstormsecurity.com/files/44613/Ubuntu-Security-Notice-264-1.html