The Apache HTTP Server is a popular web server.
It was discovered that the fix for CVE-2011-3368 (released via RHSA-2011:1391) did not completely address the problem. An attacker could bypass the fix and make a reverse proxy connect to an arbitrary server not directly accessible to the attacker by sending an HTTP version 0.9 request, or by using a specially-crafted URI. (CVE-2011-3639, CVE-2011-4317)
An integer overflow flaw, leading to a heap-based buffer overflow, was found in the way httpd performed substitutions in regular expressions. An attacker able to set certain httpd settings, such as a user permitted to override the httpd configuration for a specific directory using a ".htaccess" file, could use this flaw to crash the httpd child process or, possibly, execute arbitrary code with the privileges of the "apache" user. (CVE-2011-3607)
A flaw was found in the way httpd handled child process status information. A malicious program running with httpd child process privileges (such as a PHP or CGI script) could use this flaw to cause the parent httpd process to crash during httpd service shutdown. (CVE-2012-0031)
All httpd users should upgrade to these updated packages, which contain backported patches to correct these issues. After installing the updated packages, the httpd daemon will be restarted automatically.