PHP Error "canary mismatch on efree"

A strange error appeared in the error log in 开发者_如何学编程PHP, but the script that generated this error is often used and never generated this error, and occurred only once so far. Would anyone tell me why this happened?

Error: [client {some IP}] ALERT - canary mismatch on efree() - heap overflow detected (attacker '{some IP}', file '{some script php}')

My server: Apache/2.2.13 (FreeBSD) mod_ssl/2.2.13 OpenSSL/0.9.8k DAV/2 PHP/5.2.11 with Suhosin-Patch with PHP 5.2.11

It means that Suhosin detected a bug in PHP:

http://web.archive.org/web/20140217234227/http://www.suspekt.org/2008/10/12/suhosin-canary-mismatch-on-efree-heap-overflow-detected

Seems like a log entry without the data. Probably a malformed header which was not detected correctly.

The problem is in Suhosin-Patch. Some code structures causes such error. Either remove suhosin patch either try to figure out which part of the code causes such error.