The texImage2D implementation in the WebGL subsystem 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 does not properly restrict JSVAL_TO_OBJECT casts, which might allow remote attackers to execute arbitrary code via a crafted web page.