SOC status:Duty analyst on shift

UK Cyber Defence
VulnerabilityAnalyzed

CVE-2010-3765

Mozilla Multiple Products Remote Code Execution Vulnerability

KEVCRITICAL 9.8EPSS 83.3%

Does this matter?

Known to be exploited in the wild (CISA KEV, CISA remediation deadline 27 October 2025). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.

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.

CVSS 3.1
9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
83.28% probability · 100th percentile
CISA KEV
Listed 6 October 2025 · due 27 October 2025
Weakness
CWE-119
Affected
mozilla/firefox · mozilla/thunderbird · mozilla/seamonkey
Source
cve@mitre.org

CISA notes

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. https://www.mozilla.org/en-US/security/advisories/mfsa2010-73 ; https://nvd.nist.gov/vuln/detail/CVE-2010-3765

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.