Using the Address Sanitizer tool, security researcher Atte Kettunen from OUSPG found a heap corruption in gfxImageSurface which allows for invalid frees and possible remote code execution. This happens due to float error, resulting from graphics values being passed through different number systems. Reference: http://www.mozilla.org/security/announce/2012/mfsa2012-23.html
Acknowledgements: Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges Atte Kettunen from OUSPG as the original reporter.
This issue has been addressed in following products: Red Hat Enterprise Linux 5 Red Hat Enterprise Linux 6 Via RHSA-2012:0516 https://rhn.redhat.com/errata/RHSA-2012-0516.html
This issue has been addressed in following products: Red Hat Enterprise Linux 5 Red Hat Enterprise Linux 6 Via RHSA-2012:0515 https://rhn.redhat.com/errata/RHSA-2012-0515.html