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CVE-2025-6434VulnerabilityPublished Updated

CVE-2025-6434: Mozilla Firefox · Clickjacking

Affects Mozilla FirefoxSource CVE Database V5

0

Not known to be exploited · CVSS 4.3 Medium : upgrade to 140 when convenient.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score
4.3Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 20% 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:R/S:U/C:N/I:L/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 2026-10-25.

What to do

Upgrade Mozilla Firefox to 140.

Affected software

ProductAffectedFixed in
Mozilla FirefoxAffected
  • <140
Fixed in
  • 140

AI-suggested

This vulnerability has been fixed in Mozilla Firefox 140 and Thunderbird 140. Users and administrators should update to these versions or later to ensure the vulnerability is remediated. No additional mitigation steps are required as the fix is official and available.

Description

The exception page for the HTTPS-Only feature, displayed when a website is opened via HTTP, lacked an anti-clickjacking delay, potentially allowing an attacker to trick a user into granting an exception and loading a webpage over HTTP. This vulnerability was fixed in Firefox 140 and Thunderbird 140.

References

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