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CVE-2025-0240VulnerabilityPublished Updated

CVE-2025-0240: Mozilla Firefox · Vulnerability

Affects Mozilla FirefoxSource CVE Database V5

0

Not known to be exploited · CVSS 4.0 Medium : upgrade to 134 when convenient.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score
4.0Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.6% chance of exploitation in 30 days – higher than 51% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 134
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 7 Jan 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 2026-10-26.

What to do

Upgrade Mozilla Firefox to 134.

Affected software

ProductAffectedFixed in
Mozilla FirefoxAffected
  • <134
Fixed in
  • 134

AI-suggested

Users and administrators should update Mozilla Firefox to version 134 or later, or Firefox ESR to version 128.6 or later, where this vulnerability is fixed. Since the vendor advisory confirms an official fix is available, applying these updates is the recommended remediation. No additional mitigation steps are indicated by the vendor advisory.

Description

Parsing a JavaScript module as JSON could, under some circumstances, cause cross-compartment access, which may result in a use-after-free. This vulnerability was fixed in Firefox 134, Firefox ESR 128.6, Thunderbird 134, and Thunderbird 128.6.

References

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