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CVE-2025-0243VulnerabilityPublished Updated

CVE-2025-0243: Mozilla Firefox · Vulnerability

Affects Mozilla FirefoxSource CVE Database V5

0

Not known to be exploited · CVSS 5.1 Medium.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score
5.1Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 16% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/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

Affected software

ProductAffectedFixed in
Mozilla FirefoxAffected
  • =133
  • =128.5
Fixed in–

AI-suggested

Users and administrators should update affected Mozilla products to Firefox 134, Firefox ESR 128.6, Thunderbird 134, or Thunderbird 128.6 as appropriate. These versions contain official fixes for the memory safety bugs described. No additional mitigation steps are required beyond applying the official updates.

Description

Memory safety bugs present in Firefox 133, Thunderbird 133, Firefox ESR 128.5, and Thunderbird 128.5. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 134, Firefox ESR 128.6, Thunderbird 134, and Thunderbird 128.6.

References

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