CVE-2012-3989: Canonical Ubuntu Linux

High severity, CVSS 9.3. EPSS: 3.5% chance of exploitation in the next 30 days.

Mozilla Firefox before 16.0, Thunderbird before 16.0, and SeaMonkey before 2.13 do not properly perform a cast of an unspecified variable during use of the instanceof operator on a JavaScript object, which allows remote attackers to execute arbitrary code or cause a denial of service (assertion failure) via a crafted web site.

Affected products

• Canonical Ubuntu Linux: version 10.04 only; version 11.04 only; version 11.10 only; version 12.04 only
• Mozilla Firefox: before 16.0 (fixed in 16.0)
• Mozilla Seamonkey: before 2.13 (fixed in 2.13)
• Mozilla Thunderbird: before 16.0 (fixed in 16.0)
• Suse Linux Enterprise Desktop: version 10 only; version 11 only
• Suse Linux Enterprise Server: version 10 only; version 11 only

Published 2012-10-10. Last modified 2026-06-16.