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VulnerabilityPublished Updated

CVE-2026-100789: 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 153.4 : 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
0.3% chance of exploitation in 30 days – higher than 25% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 153.4
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
  • <153.4
  • <157
  • <140.17
  • <115.42
Fixed in
  • 153.4
  • 157
  • 140.17
  • 115.42

AI-suggested

This vulnerability has been fixed in Firefox ESR 153.4, Firefox 157, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox ESR 115.42, and Firefox ESR 140.17. Users and administrators should update to these fixed versions or later to mitigate the risk. No additional mitigations are indicated by the vendor advisory.

Description

CVE-2026-100789 is a use-after-free vulnerability in the Graphics: Canvas2D component of Mozilla Firefox and Thunderbird. This vulnerability allows for potential remote code execution or denial of service. It has been fixed in multiple versions of Firefox and Thunderbird, including Firefox ESR 153.4, Firefox 157, and Thunderbird 157 among others. The vulnerability has a high severity score of 8.8 and requires user interaction for exploitation.

References

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