From apache.org :
This follow-up to our earlier advisory is to warn of known-exploitable conditions related to this vulnerability on both 64-bit platforms and 32-bit platforms alike. Though we previously reported that 32-bit platforms were not remotely exploitable, it has since been proven by Gobbles that certain conditions allowing exploitation do exist.
Successful exploitation of this vulnerability can lead to the execution of arbitrary code on the server with the permissions of the web server child process. This can facilitate the further exploitation of vulnerabilities unrelated to Apache on the local system, potentially allowing the intruder root access.
Note that early patches for this issue released by ISS and others do not address its full scope.
Due to the existence of exploits circulating in the wild for some platforms, the risk is considered high. The Apache Software Foundation has released versions 1.3.26 and 2.0.39 that address and fix this issue, and all users are urged to upgrade immediately. These versions are available for download; see below.
If, for any reason, you are unable to upgrade at this time, as a minimum, this
http://www.apache.org/dist/httpd/patches/apply_to_1.3.22/SECURITY_chunk_size_patch.txt'>patch for httpd 1.2.0-1.3.22 should be applied to the source code.