Vulnerability in Mozilla Firefox
CVE-2026-8401
Sandbox escape in the Profile Backup component. This vulnerability was fixed in Firefox 150.0.3, Firefox ESR 115.36, Firefox ESR 140.11, and Thunderbird 140.11.
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 (47.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 47th percentile — 47.4% 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: 0.006 · change: +0.003
Affected products
- Mozilla Firefox — versions 115.36, 150.0.3, 140.11
- Mozilla Thunderbird — versions 140.11
Weakness classification (CWE)
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
- www.mozilla.org/security/advisories/mfsa2026-45/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-47/
- www.mozilla.org/security/advisories/mfsa2026-48/
- www.mozilla.org/security/advisories/mfsa2026-51/
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 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-2026-8401?
- CVE-2026-8401 is a critical-severity vulnerability in Mozilla Firefox, classified under Protection Mechanism Failure. CVSS score: 9.8/10. Published 2026-05-12.
- How severe is CVE-2026-8401?
- Critical severity. CVSS v3 base score is 9.8 out of 10.