Published: 18 January 2011
PHP before 5.3.4 accepts the \0 character in a pathname, which might allow context-dependent attackers to bypass intended access restrictions by placing a safe file extension after this character, as demonstrated by .php\0.jpg at the end of the argument to the file_exists function.
Launchpad, Ubuntu, Debian
upstream only prepared a fix for the 5.3 tree. Backporting the fix to 5.2.x requires modifying php APIs.