Vulnerability in Mozilla Firefox
CVE-2026-16363
JIT miscompilation in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
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: 0.004 (36.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 37th percentile — 36.8% 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: 0.004 · change: 0.000
Affected products
- Mozilla Firefox — versions 140.13, 153
- Mozilla Thunderbird — versions 140.13, 153
Weakness classification (CWE)
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
- www.mozilla.org/security/advisories/mfsa2026-68/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-70/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-71/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-72/ (Vendor Advisory)
Frequently asked questions
- What is CVE-2026-16363?
- CVE-2026-16363 is a critical-severity vulnerability in Mozilla Firefox, classified under Incorrect Calculation. CVSS score: 9.8/10. Published 2026-07-21.
- How severe is CVE-2026-16363?
- Critical severity. CVSS v3 base score is 9.8 out of 10.