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VulnerabilityPublished Updated

CVE-2025-6427: Mozilla Firefox · CWE-693

Affects Mozilla FirefoxSource CVE Database V5

0

Not known to be exploited · CVSS 9.1 Critical : upgrade to 140 as a priority.

Data as of 26 Oct 2026, 09:16 UTC

CVSS 3.1 base score
9.1Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 30% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 140
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 24 Jun 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: 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 26 Oct 2026.

What to do

Upgrade Mozilla Firefox to 140.

Affected software

ProductAffectedFixed in
Mozilla FirefoxAffected
  • <140
Fixed in
  • 140

AI-suggested

This vulnerability is fixed in Firefox 140 and Thunderbird 140. Users and administrators should upgrade to these versions or later to remediate the issue. No additional mitigation steps are required as the vendor advisory confirms the availability of an official fix.

Description

An attacker was able to bypass the `connect-src` directive of a Content Security Policy by manipulating subdocuments. This would have also hidden the connections from the Network tab in Devtools. This vulnerability was fixed in Firefox 140 and Thunderbird 140.

References

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