Severity: Critical
CVSS Score: 10
The gfxSkipCharsIterator::SetOffsets function in Mozilla Firefox before 21.0, Firefox ESR 17.x before 17.0.6, Thunderbird before 17.0.6, and Thunderbird ESR 17.x before 17.0.6 allows remote attackers to execute arbitrary code or cause a denial of service (out-of-bounds read) via unspecified vectors.