CVE-2026-100800: Mozilla Firefox · Use After Free
Affects Mozilla FirefoxSource CVE Database V5
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
- 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:HExploitation evidence
Disclosed: evidence found.
CVE published 29 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| Mozilla Firefox | Affected
| Fixed in
|
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
- bugzilla.mozilla.org/show_bug.cgi?id=2056767 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-100/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-97/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-101/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-103/ (opens in a new tab)