The cairo-dwrite implementation in Mozilla Firefox 4.x through 11.0, Firefox ESR 10.x before 10.0.4, Thunderbird 5.0 through 11.0, Thunderbird ESR 10.x before 10.0.4, and SeaMonkey before 2.9, when certain Windows Vista and Windows 7 configurations are used, does not properly restrict font-rendering attempts, which allows remote attackers to cause a denial of service (memory corruption) or possibly execute arbitrary code via unspecified vectors.