Buffer overflow in Mozilla Firefox
CVE-2026-4690
Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Vulnerability class: Integer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.6 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.008 (53.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 54th percentile — 53.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000
Affected products
- Mozilla Firefox — versions 115.34, 140.9, 149
- Mozilla Thunderbird — versions 140.9, 149
Weakness classification (CWE)
References
- bugzilla.mozilla.org/show_bug.cgi (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-20/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-21/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-22/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-23/
- www.mozilla.org/security/advisories/mfsa2026-24/
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Frequently asked questions
- What is CVE-2026-4690?
- CVE-2026-4690 is a high-severity vulnerability in Mozilla Firefox, classified under Integer Overflow or Wraparound. CVSS score: 8.6/10. Published 2026-03-24.
- How severe is CVE-2026-4690?
- High severity. CVSS v3 base score is 8.6 out of 10.