Buffer overflow in Mozilla Firefox
CVE-2025-0243
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.1 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (15.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 15th percentile — 15.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- Mozilla Firefox — versions 128.6, 134
- Mozilla Thunderbird — versions 128.6, 134
Weakness classification (CWE)
References
- bugzilla.mozilla.org/buglist.cgi (Issue Tracking, Broken Link)
- 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-2025-0243?
- CVE-2025-0243 is a medium-severity vulnerability in Mozilla Firefox, classified under Out-of-bounds Write. CVSS score: 5.1/10. Published 2025-01-07.
- How severe is CVE-2025-0243?
- Medium severity. CVSS v3 base score is 5.1 out of 10.