There is a new exploit that affects how Apple QuickTime handles the Real Time Streaming Protocol (RTSP) and may allow an attacker to execute arbitrary code or cause a denial-of-service attack on a vulnerable system. The condition is similar yet different from a QuickTime RTSP flaw reported in December. This new vulnerability can occur on a fully patched QuickTime version 7.3.1, running on Windows and possibly Mac OS X.
Discovered by Luigi Auriemma, details can be found here, and here. Auriemma provides an exploit example on his site and writes: "For exploiting this vulnerability is only needed that an user follows a rtsp:// link, if the port 554 of the server is closed QuickTime will automatically change the transport and will try the HTTP protocol on port 80, the 404 error message of the server (other error numbers are valid too) will be visualized in the LCD-like screen."
Apple has not said when a patch for this will become available.