The version of mod_proxy shipped with Apache 1.3.31 and possibly earlier versions are susceptible to a buffer overflow via the Content-Length: header. This can lead to a denial of service and possible compromise of a vulnerable system.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/33547/modproxy1.html
Source: https://packetstormsecurity.com/files/33547/modproxy1.html.html