K20979231 : Apache vulnerability CVE-2011-3639

Security Advisory Description

The mod_proxy module in the Apache HTTP Server 2.0.x through 2.0.64 and 2.2.x before 2.2.18, when the Revision 1179239 patch is in place, does not properly interact with use of (1) RewriteRule and (2) ProxyPassMatch pattern matches for configuration of a reverse proxy, which allows remote attackers to send requests to intranet servers by using the HTTP/0.9 protocol with a malformed URI containing an initial @ (at sign) character. NOTE: this vulnerability exists because of an incomplete fix for CVE-2011-3368. (CVE-2011-3639)
Impact
An attacker could make a reverse proxy connect to an arbitrary server that is not directly accessible to the attacker by sending an HTTP version 0.9 request to a vulnerable Apache HTTP server.