CVE-2026-4701
CRITICALCVSS 9.8/10EPSS 0.46%
Last modified
CVE-2026-4701 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.. EPSS estimates a 0.46% chance of exploitation in the next 30 days.
Description
Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | < 140.9.0 |
| Mozilla | Firefox | < 149.0 |
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2009303Permissions Required
- https://www.mozilla.org/security/advisories/mfsa2026-20/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-22/Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is CVE-2026-4701?
Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
How severe is CVE-2026-4701?
CVE-2026-4701 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.46% probability of exploitation in the next 30 days.
How do I fix CVE-2026-4701?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.
Are you affected by CVE-2026-4701?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST