Security researcher Jordi Chancel reported that a JPEG image could be constructed that would be decoded incorrectly, causing data to be written past the end of a buffer created to store the image. An attacker could potentially craft such an image that would cause malicious code to be stored in memory and then later executed on a victim's computer.
This is now public: http://www.mozilla.org/security/announce/2011/mfsa2011-09.html
This issue has been addressed in following products: Red Hat Enterprise Linux 6 Via RHSA-2011:0311 https://rhn.redhat.com/errata/RHSA-2011-0311.html
This issue has been addressed in following products: Red Hat Enterprise Linux 4 Red Hat Enterprise Linux 5 Red Hat Enterprise Linux 6 Via RHSA-2011:0310 https://rhn.redhat.com/errata/RHSA-2011-0310.html