The dechunk filter in PHP 5.3 through 5.3.2, when decoding an HTTP chunked encoding stream, allows context-dependent attackers to cause a denial of service (crash) and possibly trigger memory corruption via a negative chunk size, which bypasses a signed comparison, related to an integer overflow in the chunk size decoder.
http://lists.opensuse.org/opensuse-security-announce/2010-09/msg00006.html