Use After Free in Mozilla Firefox
CVE-2025-0240
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.
Vulnerability class: Use-After-Free
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.0 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.
EPSS exploit prediction
EPSS: 0.007 (50.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 50.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000
Affected products
- Mozilla Firefox — versions 128.6, 134
- Mozilla Thunderbird — versions 128.6, 134
Weakness classification (CWE)
Public proof-of-concept exploits
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required, Issue Tracking)
- www.mozilla.org/security/advisories/mfsa2025-01/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-02/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-04/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-05/ (Vendor Advisory)
- af854a3a-2127-422b-91ae-364da2661108
Frequently asked questions
- What is CVE-2025-0240?
- CVE-2025-0240 is a medium-severity vulnerability in Mozilla Firefox, classified under Use After Free. CVSS score: 4.0/10. Published 2025-01-07.
- How severe is CVE-2025-0240?
- Medium severity. CVSS v3 base score is 4.0 out of 10.
- Is CVE-2025-0240 known to be exploited?
- 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.