Integer overflow in Mozilla Firefox
CVE-2026-2781
Integer overflow in the Libraries component in NSS. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, Thunderbird 140.8, and Firefox ESR 115.35.
Vulnerability class: Integer Overflow
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: 0.006 (44.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 44th percentile — 44.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.006 · change: +0.002
Affected products
- Mozilla Firefox — versions 115.35, 140.8, 148
- Mozilla Thunderbird — versions 140.8, 148
Weakness classification (CWE)
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required, Issue Tracking)
- www.mozilla.org/security/advisories/mfsa2026-13/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-15/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-16/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-17/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-31/
- af854a3a-2127-422b-91ae-364da2661108
Frequently asked questions
- What is CVE-2026-2781?
- CVE-2026-2781 is a critical-severity vulnerability in Mozilla Firefox, classified under Integer Overflow or Wraparound. CVSS score: 9.8/10. Published 2026-02-24.
- How severe is CVE-2026-2781?
- Critical severity. CVSS v3 base score is 9.8 out of 10.