CVE-2010-3765
CVE-2010-3765 is a security flaw in Mozilla products, Mozilla’s web browser. Attackers can run their own code on Mozilla products. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 6 Oct 2025.[1]
Mozilla products is in things households have, such as phones, computers, browsers and everyday apps, so the fix matters at home as much as at work. Mozilla has published a fix or advice.
Description
CISA calls it a remote code execution in Mozilla Multiple Products. In its words: “Mozilla Firefox, SeaMonkey, and Thunderbird contain an unspecified vulnerability when JavaScript is enabled. This 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.”[1]
The CVE record adds: “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.”[2]
The underlying weakness is memory buffer error (CWE-119), in MITRE’s list of common software weaknesses.
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by the organisation that published the CVE using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Mozilla’s advisory has them[3]. CISA names the product as Mozilla Multiple Products.
Every device with Mozilla products needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 6 Oct 2025, 5,457 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 27 Oct 2025 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 83%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Mozilla has published a fix or advice.[3] CISA’s required action: “Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.”[1]
- Update Mozilla products now.Install the latest update from Mozilla on every device that has it, and restart when asked. Then turn on automatic updates, so the next fix arrives on its own.
- If there’s no update, stop using it.CISA’s advice when a flaw being used in attacks has no fix is to stop using the product until it does.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 9.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 83%.[4] |
See also
Other Mozilla flaws
- CVE-2024-9680, Mozilla Firefox: use-after-free ·
- CVE-2016-9079, Mozilla Firefox, Firefox ESR, and Thunderbird: use-after-free ·
- CVE-2015-4495, Mozilla Firefox: security feature bypass ·
- CVE-2019-11708, Mozilla Firefox and Thunderbird: sandbox escape ·
- CVE-2019-11707, Mozilla Firefox and Thunderbird: type confusion ·
Other memory buffer error flaws
- CVE-2026-88779, Citrix NetScaler: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2026-88772, Citrix NetScaler: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2026-88771, Citrix NetScaler: improper input validation ·
- CVE-2026-8452, Citrix NetScaler ADC and NetScaler Gateway: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2009-3459, Adobe Acrobat and Reader: heap-based buffer overflow ·
Added the same day
- CVE-2025-61882, Oracle E-Business Suite: unspecified ·
- CVE-2021-43226, Microsoft Windows: privilege escalation ·
- CVE-2021-22555, Linux Kernel: heap out-of-bounds write ·
- CVE-2013-3918, Microsoft Windows: out-of-bounds write ·
- CVE-2011-3402, Microsoft Windows: remote code execution ·
Every Mozilla flaw on CISA’s list · Everything added in October 2025
References
- ^ Cybersecurity and Infrastructure Security Agency. “Mozilla Multiple Products Remote Code Execution Vulnerability”. Known Exploited Vulnerabilities Catalog, added 6 Oct 2025.
- ^ National Institute of Standards and Technology. “CVE-2010-3765 Detail”. National Vulnerability Database, published 28 Oct 2010.
- ^ Mozilla. Advisories and fixes: mozilla.org.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.832, percentile 99.7, 31 Oct 2026.
- CVE Program. “CVE-2010-3765”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.