Description of problem:
PHP 4.x and 5.x before 5.2.1, when running on multi-threaded systems, does not
ensure thread safety for libc crypt function calls using protection schemes such
as a mutex, which creates race conditions that allow remote attackers to
overwrite internal program memory and gain system access.

http://nvd.nist.gov/nvd.cfm?cvename=CVE-2007-2844
http://blog.php-security.org/archives/82-Suhosin-0.9.20-and-crypt-Thread-Safety-Vulnerability.html