CVE-2010-3765: Mozilla Multiple Products Remote Code Execution Vulnerability

Critical severity, CVSS 9.8. Actively exploited: in CISA KEV since 2025-10-06. EPSS: 83.2% chance of exploitation in the next 30 days.

Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before 3.1.6 and 3.0.x before 3.0.10, and SeaMonkey 2.x before 2.0.10, when JavaScript is enabled, allows remote attackers to execute arbitrary code via vectors related to nsCSSFrameConstructor::ContentAppended, the appendChild method, incorrect index tracking, and the creation of multiple frames, which triggers memory corruption, as exploited in the wild in October 2010 by the Belmoo malware.

Affected products

• Mozilla Firefox: version 3.5 only; version 3.5.1 only; version 3.5.2 only; version 3.5.3 only; version 3.5.4 only; version 3.5.5 only; …
• Mozilla Seamonkey: version 2.0 only; version 2.0.1 only; version 2.0.2 only; version 2.0.3 only; version 2.0.4 only; version 2.0.5 only; …
• Mozilla Thunderbird: version 3.0.1 only; version 3.0.2 only; version 3.0.3 only; version 3.0.4 only; version 3.0.5 only; version 3.0.6 only; …

Published 2010-10-28. Last modified 2026-06-16.