CVE-2010-3765 — Red Hat
CRITICALCVE-2010-3765 is a critical-severity (CVSS 9.8) Buffer Overflow vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2025-10-06) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.
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…
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2025-10-06. Federal agencies were required to remediate by 2025-10-27.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2010-3765.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2010-3765 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).
Where this sits among everything scored
Of 395,308 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Counts from FIRST.org, log-scaled.
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.
Affected Products
firefoxmozillaseamonkeymozillathunderbirdmozillaResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Mozilla Firefox - Simplified Memory Corruption (PoC)
by extraexploit · Oct 28, 2010
Mozilla Firefox - Interleaving 'document.write' / 'appendChild' Denial of Service
by Daniel Veditz · Oct 28, 2010
Mozilla Firefox - Interleaving 'document.write' / 'appendChild' (Metasploit)
by Metasploit · Feb 22, 2011
Mozilla Firefox 3.6.8 < 3.6.11 - Interleaving 'document.write' / 'appendChild' Remote Overflow
by anonymous · Oct 29, 2010
Detection & mitigation playbook
VulnerabilityDetect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Remediation status
No fixed release is recorded for CVE-2010-3765 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.
Mitigate without a patch
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 3 | seamonkey-0:1.0.9-0.62.el3 | RHSA-2010:0810 |
| Red Hat Enterprise Linux 4 | firefox-0:3.6.11-4.el4_8 | RHSA-2010:0808 |
| Red Hat Enterprise Linux 4 | thunderbird-0:1.5.0.12-33.el4 | RHSA-2010:0812 |
| Red Hat Enterprise Linux 5 | xulrunner-0:1.9.2.11-4.el5_5 | RHSA-2010:0809 |
| Red Hat Enterprise Linux 6 | firefox-0:3.6.12-1.el6_0 | RHSA-2010:0861 |
| Red Hat Enterprise Linux 6 | thunderbird-0:3.1.6-1.el6_0 | RHSA-2010:0896 |
Frequently Asked Questions
Is CVE-2010-3765 in your dependencies?
Find it across , including transitive dependencies.