Use After Free in Mozilla Firefox
CVE-2025-6424
A use-after-free in FontFaceSet resulted in a potentially exploitable crash. This vulnerability was fixed in Firefox 140, Firefox ESR 115.25, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.
Vulnerability class: Use-After-Free
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.044 (91.0th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 91st percentile — 91.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.034 · newest: 0.044 · change: +0.010
Affected products
- Mozilla Firefox — versions 115.25, 128.12, 140
- Mozilla Thunderbird — versions 128.12, 140
Weakness classification (CWE)
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
- www.mozilla.org/security/advisories/mfsa2025-51/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-52/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-53/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-54/
- www.mozilla.org/security/advisories/mfsa2025-55/
- af854a3a-2127-422b-91ae-364da2661108
- af854a3a-2127-422b-91ae-364da2661108
Frequently asked questions
- What is CVE-2025-6424?
- CVE-2025-6424 is a critical-severity vulnerability in Mozilla Firefox, classified under Use After Free. CVSS score: 9.8/10. Published 2025-06-24.
- How severe is CVE-2025-6424?
- Critical severity. CVSS v3 base score is 9.8 out of 10.