Ubuntu Security Notice USN-6885-3

Ubuntu Security Notice 6885-3 - USN-6885-1 fixed several vulnerabilities in Apache. This update provides the corresponding update for Ubuntu 16.04 LTS and Ubuntu 18.04 LTS. Orange Tsai discovered that the Apache HTTP Server mod_rewrite module incorrectly handled certain substitutions. A remote attacker could possibly use this issue to execute scripts in directories not directly reachable by any URL, or cause a denial of service. Some environments may require using the new UnsafeAllow3F flag to handle unsafe substitutions.