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VulnerabilityPublished Updated

CVE-2026-6771: Mozilla Firefox · CWE-288

Affects Mozilla FirefoxSource CVE Database V5

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Not known to be exploited · CVSS 9.8 Critical · patch available : patch Mozilla Firefox as a priority.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.

Contested

Critical score, yet low EPSS after six months
EPSS
0.3% chance of exploitation in 30 days – higher than 23% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 21 Apr 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 30 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
Mozilla FirefoxAffected
  • <150
Fixed in
  • 150

AI-suggested

Mozilla has released official fixes for this vulnerability in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird ESR 140.10. Users and administrators should upgrade to these versions or later to remediate the vulnerability. Since the vendor advisory confirms the fix availability, no additional mitigation steps are required beyond applying the official updates.

Description

Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

References

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