Ubuntu Security Notice USN-177-1 – apache2, libapache-mod-ssl vulnerabilities – Apache did not honour the “SSLVerifyClient require” directive within a block if the surrounding block contained a directive “SSLVerifyClient optional”. This allowed clients to bypass client certificate validation on servers with the above configuration. Also, Filip Sneppe discovered a Denial of Service vulnerability in the byte range filter handler. By requesting certain large byte ranges, a remote attacker could cause memory exhaustion in the server.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/39907/USN-177-1.txt
Source: https://packetstormsecurity.com/files/39907/Ubuntu-Security-Notice-177-1.html