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VulnerabilityPublished Updated

CVE-2026-100800: Mozilla Firefox · Use After Free

Affects Mozilla FirefoxSource CVE Database V5

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Not known to be exploited · CVSS 9.6 Critical · fixed in 153.4 : patch Mozilla Firefox as a priority.

Data as of 12 Nov 2026, 23:24 UTC

CVSS 3.1 base score
9.6Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 22% 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:C/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
Fixed in
  • 153.4

AI-suggested

Mozilla has released official fixes for this vulnerability in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157. Users and administrators should update to these versions or later to remediate the issue. Patch status is confirmed by Mozilla advisories. No additional mitigation is required once updated.

Description

CVE-2026-100800 is a critical use-after-free vulnerability in the Disability Access APIs component of Mozilla Firefox that allows sandbox escape. This flaw was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157. The vulnerability has a high CVSS score of 9.6, indicating severe impact on confidentiality, integrity, and availability. No known exploits are reported in the wild at this time.

References

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