# CVE-2010-3765: Mozilla Multiple Products memory corruption in nsCSSFrameConstructor

Source: https://junglewise.ai/threats/cve-2010-3765-mozilla-multiple-products-memory-corruption-in  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2025-10-06. Updated: 2026-05-15  
License: CC BY 4.0 with a link back

CVE-2010-3765 · Severity: critical · CVSS 9.8 · Exploited in the wild · Published 2025-10-06

Mozilla Firefox, Thunderbird, and SeaMonkey are popular web browsers and email clients. A critical vulnerability allows an attacker to take complete control of a user's computer if they visit a malicious website or view a specially crafted email while JavaScript is enabled. This flaw has been actively exploited in the wild to install malware.

Technologies: [Apple Multiple Products](https://junglewise.ai/threats/technologies/multiple-products), [Mozilla Firefox](https://junglewise.ai/threats/technologies/firefox), [Mozilla Thunderbird](https://junglewise.ai/threats/technologies/thunderbird). Vendors: [Apple](https://junglewise.ai/threats/vendors/apple), [Mozilla](https://junglewise.ai/threats/vendors/mozilla).

## Quick answers

**Is CVE-2010-3765 exploited in the wild?** Yes. CVE-2010-3765 is known to be exploited in the wild, first recorded on 6 October 2025. Treat it as urgent.

**How severe is CVE-2010-3765?** Critical severity, with a CVSS score of 9.8, published 6 October 2025.

**Which products and versions are affected?** Mozilla Firefox 3.5.x through 3.5.14, 3.6.x through 3.6.11; Mozilla SeaMonkey 2.x before 2.0.10; Mozilla Thunderbird 3.1.6 before 3.1.6, 3.0.x before 3.0.10.

**Is there a fix for CVE-2010-3765?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2010-3765 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2010-3765?** Check whether you run Apple Multiple Products, Mozilla Firefox, Mozilla SeaMonkey or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A memory corruption vulnerability exists in Mozilla products due to incorrect index tracking within the nsCSSFrameConstructor::ContentAppended function. When JavaScript is enabled, an attacker can trigger this flaw using the appendChild method and the creation of multiple frames to cause a buffer overflow or similar memory corruption. This allows for remote code execution (RCE) without user interaction beyond visiting a malicious page. The vulnerability was notably exploited in the wild by the Belmoo malware. Patches were released in late 2010 for the affected versions.

## Affected products

- Mozilla Firefox 3.5.x through 3.5.14, 3.6.x through 3.6.11
- Mozilla Thunderbird 3.1.6 before 3.1.6, 3.0.x before 3.0.10
- Mozilla SeaMonkey 2.x before 2.0.10

## Timeline

- 2010-10-26: advisory: Mozilla security blog post published
- 2010-10-27: exploited: Exploited in the wild by Belmoo malware
- 2025-10-06: kev added: Added to CISA Known Exploited Vulnerabilities catalog

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