CVE-2026-4723

Name: CVE-2026-4723
Creator: NVD / NIST
Published: 2026-03-24T13:16:08.19+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 0.39%

Last modified Jun 17, 2026

CVE-2026-4723 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 and Thunderbird 149.. EPSS estimates a 0.39% chance of exploitation in the next 30 days.

Description

Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 149 and Thunderbird 149.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

0.39%

31.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 149.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2013573Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-20/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-23/

Timeline

Published: Mar 24, 2026
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2026-4723?

Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 149 and Thunderbird 149.

How severe is CVE-2026-4723?

CVE-2026-4723 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.39% probability of exploitation in the next 30 days.

How do I fix CVE-2026-4723?

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-2026-4723?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST