PHP is an HTML-embedded scripting language commonly used with the Apache HTTP Server. It was found that the hashing routine used by PHP arrays was susceptible to predictable hash collisions. If an HTTP POST request to a PHP application contained many parameters whose names map to the same hash value, a large amount of CPU time would be consumed. This flaw has been mitigated by adding a new configuration directive, max_input_vars, that limits the maximum number of parameters processed per request. By default, max_input_vars is set to 1000. A use-after-free flaw was found in the PHP substr_replace function. If a PHP script used the same variable as multiple function arguments, a remote attacker could possibly use this to crash the PHP interpreter or, possibly, execute arbitrary code. An integer overflow flaw was found in the PHP exif extension. On 32-bit systems, a specially-crafted image file could cause the PHP interpreter to crash or disclose portions of its memory when a PHP script tries to extract Exchangeable image file format metadata from the image file. An insufficient input validation flaw, leading to a buffer over-read, was found in the PHP exif extension. A specially-crafted image file could cause the PHP interpreter to crash when a PHP script tries to extract Exchangeable image file format metadata from the image file. An integer overflow flaw was found in the PHP calendar extension. A remote attacker able to make a PHP script call SdnToJulian with a large value could cause the PHP interpreter to crash. A bug in the PHP Streams component caused the PHP interpreter to crash if an FTP wrapper connection was made through an HTTP proxy. A remote attacker could possibly trigger this issue if a PHP script accepted an untrusted URL to connect to. An off-by-one flaw was found in PHP. If an attacker uploaded a file with a specially-crafted file name it could cause a PHP script to attempt to write a file to the root directory. By default, PHP runs as the "apache" user, preventing it from writing to the root directory. Red Hat would like to thank oCERT for reporting CVE-2011-4885. oCERT acknowledges Julian Wlde and Alexander Klink as the original reporters of CVE-2011-4885. All php users should upgrade to these updated packages, which contain backported patches to resolve these issues. After installing the updated packages, the httpd daemon must be restarted for the update to take effect.