CVE-2011-3661: Mozilla Firefox

High severity, CVSS 7.5. EPSS: 3.7% chance of exploitation in the next 30 days.

YARR, as used in Mozilla Firefox 4.x through 8.0, Thunderbird 5.0 through 8.0, and SeaMonkey before 2.6, allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code via crafted JavaScript.

Affected products

• Mozilla Firefox: version 4.0 only; version 4.0.1 only; version 5.0 only; version 5.0.1 only; version 6.0 only; version 6.0.1 only; …
• Mozilla Seamonkey: up to and including 2.5; 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: version 5.0 only; version 6.0 only; version 6.0.1 only; version 6.0.2 only; version 7.0 only; version 7.0.1 only; …

Published 2011-12-21. Last modified 2026-06-16.