Vulnerability in Mozilla Firefox
CVE-2026-6763
Mitigation bypass in the File Handling component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (22.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 23rd percentile — 22.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001
Affected products
- Mozilla Firefox — versions 140.10, 150
- Mozilla Thunderbird — versions 140.10, 150
Weakness classification (CWE)
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
- www.mozilla.org/security/advisories/mfsa2026-30/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-32/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-33/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-34/ (Vendor Advisory)
Frequently asked questions
- What is CVE-2026-6763?
- CVE-2026-6763 is a medium-severity vulnerability in Mozilla Firefox, classified under Protection Mechanism Failure. CVSS score: 6.5/10. Published 2026-04-21.
- How severe is CVE-2026-6763?
- Medium severity. CVSS v3 base score is 6.5 out of 10.