Red Hat Security Advisory 2015-0165-01 – Subversion is a concurrent version control system which enables one or more users to collaborate in developing and maintaining a hierarchy of files and directories while keeping a history of all changes. The mod_dav_svn module is used with the Apache HTTP Server to allow access to Subversion repositories via HTTP. A NULL pointer dereference flaw was found in the way the mod_dav_svn module handled REPORT requests. A remote, unauthenticated attacker could use a specially crafted REPORT request to crash mod_dav_svn. It was discovered that Subversion clients retrieved cached authentication credentials using the MD5 hash of the server realm string without also checking the server’s URL. A malicious server able to provide a realm that triggers an MD5 collision could possibly use this flaw to obtain the credentials for a different realm.