Via this Secunia advisory posted today, there's information about the update the Fedora Linux group has made to the PHP package included in their distribution. According to the release:

This fixes some vulnerabilities, which can be exploited by malicious, local users to bypass certain security restrictions and by malicious people to bypass certain security restrictions and cause a DoS (Denial of Service).

The original advisory post has more details on what the update fixes as well as the link to download the RPM packages to update your system. You can either manually download them or use the "yum" system to handle things a bit more automatically.