GEN:SID 1:2580
Message WEB-MISC server negative Content-Length attempt
Summary This event is generated when an attempt is made to exploit a heap overflow
associated with Apache 1.3 proxy and cache module.
Impact A successful attack may cause a heap overflow, permitting the execution of
arbitrary code.
Detailed Information When Apache 1.3 is used and the host is configured to be a web proxy,
reverse proxy and/or cache server, a vulnerability exists that may
allow a heap overflow and the subsequent execution of arbitrary code
on the vulnerable server.  This may occur when the server receives
a malformed response from a malicious web server that includes a
negative content length value.  This can cause invalid memory access
and a denial of service or heap overflow.
Affected Systems Apache 1.3.x
Attack Scenarios An attacker can entice a user to visit a malicious web server.  If
a vulnerable server proxies the request and receives a malformed
response, a heap overflow may occur.
Ease of Attack Simple. Exploit code is publicly available.
Corrective Action Upgrade to the latest non-affected version of the software.
Additional References  
Rule References cve: 2004-0492
url: www.guninski.com/modproxy1.html