A vulnerability has been reported for PHP versions 4.2.0 and 4.2.1. It is possible for a remote attacker to cause the PHP interpreter to crash the web server on a vulnerable system and execute malicious, attacker supplied code.
The vulnerability is the result of the PHP interpreter incorrectly parsing MIME headers when HTTP POST commands are received. When PHP receives a malformed POST request, it generates an error condition that is improperly handled. As a result, the attacker may cause the web server to crash and possibly execute supplied code.
Also, PHP does not perform proper bounds checking on in functions related to Form-based File Uploads in HTML (RFC1867). Specifically, this problem occurs in the functions which are used to decode MIME encoded files. As a result, it may be possible to overrun the buffer used for the vulnerable functions to cause arbitrary attacker-supplied instructions to be executed.