CVE-2012-3966: Mozilla Firefox

High severity, CVSS 10.0. EPSS: 5.2% chance of exploitation in the next 30 days.

Mozilla Firefox before 15.0, Firefox ESR 10.x before 10.0.7, Thunderbird before 15.0, Thunderbird ESR 10.x before 10.0.7, and SeaMonkey before 2.12 allow remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a negative height value in a BMP image within a .ICO file, related to (1) improper handling of the transparency bitmask by the nsICODecoder component and (2) improper processing of the alpha channel by the nsBMPDecoder component.

Affected products

• Mozilla Firefox: version 10.0 only; version 10.0.1 only; version 10.0.2 only; version 10.0.3 only; version 10.0.4 only; version 10.0.5 only; …
• Mozilla Seamonkey: up to and including 2.11; version 2.0 only; version 2.0.1 only; version 2.0.2 only; version 2.0.3 only; version 2.0.4 only; …
• Mozilla Thunderbird: up to and including 14.0; version 1.0 only; version 1.0.1 only; version 1.0.2 only; version 1.0.3 only; version 1.0.4 only; …
• Mozilla Thunderbird ESR: version 10.0 only; version 10.0.1 only; version 10.0.2 only; version 10.0.3 only; version 10.0.4 only; version 10.0.5 only; …

Published 2012-08-29. Last modified 2026-06-16.