Use-after-free vulnerability in the nsSMILTimeValueSpec::IsEventBased function in Mozilla Firefox 4.x through 13.0, Firefox ESR 10.x before 10.0.6, Thunderbird 5.0 through 13.0, Thunderbird ESR 10.x before 10.0.6, and SeaMonkey before 2.11 allows remote attackers to cause a denial of service (heap memory corruption) or possibly execute arbitrary code by interacting with objects used for SMIL Timing.