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VulnerabilityPublished Updated

CVE-2026-100832: Mozilla Firefox · Use After Free

Affects Mozilla FirefoxSource CVE Database V5

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Not known to be exploited · CVSS 8.8 High · fixed in 115.42 : patch Mozilla Firefox soon.

Data as of 12 Nov 2026, 23:24 UTC

CVSS 3.1 base score
8.8High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 15% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 115.42
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 29 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
Mozilla FirefoxAffected
  • <115.42
  • <140.17
  • <153.4
Fixed in
  • 115.42
  • 140.17
  • 153.4

AI-suggested

Users should update to the fixed versions of Firefox ESR (115.42, 140.17, or 153.4) or Thunderbird (140.17 or 153.4) as soon as possible. These updates contain the official fixes for this vulnerability. No other mitigations are specified by Mozilla.

Description

CVE-2026-100832 is a use-after-free vulnerability in the Graphics: Canvas2D component of Mozilla Firefox and Thunderbird. It allows for potential remote code execution or other impacts due to improper memory handling. The issue has been fixed in Firefox ESR versions 115.42, 140.17, and 153.4, as well as Thunderbird versions 140.17 and 153.4.

References

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