The cache_invalidate function in modules/cache/cache_storage.c in the mod_cache module in the Apache HTTP Server 2.4.6, when a caching forward proxy is enabled, allows remote HTTP servers to cause a denial of service (NULL pointer dereference and daemon crash) via vectors that trigger a missing hostname value.
https://bugzilla.redhat.com/show_bug.cgi?id=1120604
http://svn.apache.org/viewvc/httpd/httpd/trunk/modules/cache/cache_storage.c