Ubuntu Security Notice 3177-2 – USN-3177-1 fixed vulnerabilities in Tomcat. The update introduced a regression in environments where Tomcat is started with a security manager. This update fixes the problem. It was discovered that the Tomcat realm implementations incorrectly handled passwords when a username didn’t exist. A remote attacker could possibly use this issue to enumerate usernames. This issue only applied to Ubuntu 12.04 LTS, Ubuntu 14.04 LTS and Ubuntu 16.04 LTS. Alvaro Munoz and Alexander Mirosh discovered that Tomcat incorrectly limited use of a certain utility method. A malicious application could possibly use this to bypass Security Manager restrictions. Various other issues were also addressed.