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vulnerability

CVE-2010-3765

9.8
Critical
KEV · Exploited in wildEPSS 83%Patch available

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.

exploited
Yes, in CISA KEV since 6 Oct 2025fix by 27 Oct 2025 (CISA deadline for US federal agencies)public exploit code
fix
Patch available see the advisory in the references
likelihood
EPSS 83.2%
Published 28 Oct 2010Analysed here 2 Nov 2026CVSS scored by CISA

do firstApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

triage
server-sideruntimeWAF can block: noAV · networkCWE-119· Buffer Boundary Error

Can a WAF block it? No. The vulnerability is triggered by JavaScript code executed in the browser, which is delivered via HTTP requests such as web pages. The malicious input looks like normal JavaScript and web content, so a web application firewall cannot reliably distinguish it from legitimate traffic.

Also consider: patch

Based on an AI reading of the CVE description, and no vendor rule found yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.

cvss vector
attack vectornetworkattack complexitylowprivileges requirednoneuser interactionnonescopeunchangedconfidentialityhighintegrityhighavailabilityhigh
CVSS 3.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
common questions

Is CVE-2010-3765 being exploited?

Yes. CVE-2010-3765 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.

How severe is CVE-2010-3765?

CVE-2010-3765 is rated Critical with a CVSS score of 9.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.

Is there a patch for CVE-2010-3765?

Yes. A fix has been recorded for CVE-2010-3765. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.

What does CVE-2010-3765 affect?

CVE-2010-3765 affects mozilla:firefox, mozilla:thunderbird, mozilla:seamonkey. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.

Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.

executive summary
technical analysis
affected
mozilla:firefoxmozilla:thunderbirdmozilla:seamonkey

public exploits

Public exploit code: 4 on Exploit-DB · 1 Metasploit module

Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.

cisa ssvc

exploitation
active
automatable
yes
technical impact
total

Assessed by CISA 4 Oct 2025 (SSVC 2.0.3).

timeline

  1. 28 Oct 2010First public exploit or proof of concept
  2. 28 Oct 2010Published · same day later
  3. 4 Oct 2025CISA SSVC assessment: exploitation active · 5,455 days (about 15 years) later
  4. 6 Oct 2025Added to CISA KEV (exploited in the wild) · 2 days later
  5. 22 Oct 2025CVE record last updated · 16 days later
  6. 27 Oct 2025CISA remediation due date (US federal agencies) · 5 days later
  7. 2 Nov 2026Analysed by vulneraibility.com · 372 days (about 1 year) later
how to fix
Remediation steps are tailored for users whose stack is affected. Add this technology to your stack to see the fix checklist.
references
50 references in the CVE record: 26 advisories, 3 exploits, 21 links
Show 42 more

sources

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