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VulnerabilityPublished Updated

CVE-2026-100770: Mozilla Firefox · Use After Free

Affects Mozilla FirefoxSource CVE Database V5

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Not known to be exploited · CVSS 9.6 Critical.

Data as of 13 Nov 2026, 23:53 UTC

CVSS 3.1 base score
9.6Critical
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.
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
  • <157
  • <140.17
Fixed in
  • 153.4
  • 157
  • 140.17

AI-suggested

Mozilla has released official patches fixing this vulnerability in Firefox ESR 153.4, Firefox 157, Thunderbird 140.17, 153.4, and 157. Users and administrators should apply these updates promptly to mitigate the risk. No additional mitigation steps are indicated beyond applying the official fixes.

Description

CVE-2026-100770 is a critical use-after-free vulnerability in the DOM Content Processes component of Mozilla Firefox that allows sandbox escape. This flaw was addressed and fixed in multiple Mozilla products including Firefox ESR 153.4, Firefox 157, and Thunderbird versions 140.17, 153.4, and 157. The vulnerability has a high CVSS score of 9.6, indicating severe impact on confidentiality, integrity, and availability.

References

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