CVE-2010-3765

CVE-2010-3765 is a critical-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 9.8. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2025-10-06). The underlying weakness is classified as CWE-119.

Key facts

Description

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.

Frequently asked questions

What is CVE-2010-3765?
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.
How severe is CVE-2010-3765?
CVE-2010-3765 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2010-3765 being actively exploited?
Yes. CVE-2010-3765 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2025-10-06, which means active exploitation has been confirmed. It should be prioritised for remediation.
What products are affected by CVE-2010-3765?
CVE-2010-3765 primarily affects Mozilla Firefox. In total, 56 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2010-3765?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.
Does CVE-2010-3765 have an EU (EUVD) identifier?
Yes. CVE-2010-3765 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2010-3744. It is also flagged as exploited in the EUVD (since 2025-10-06).
When was CVE-2010-3765 published?
CVE-2010-3765 was published on 2010-10-28 and last updated on 2026-06-16.

References

Affected products (56)

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