CVE-2026-4692

Name: CVE-2026-4692
Creator: NVD / NIST
Published: 2026-03-24T13:16:05.04+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 10/10EPSS 0.39%

Last modified Jun 17, 2026

CVE-2026-4692 is a critical-severity vulnerability rated 10/10 on the CVSS scale. Sandbox escape in the Responsive Design Mode component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.. EPSS estimates a 0.39% chance of exploitation in the next 30 days.

Description

Sandbox escape in the Responsive Design Mode component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

Metrics

CVSS 3.1

10/10

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

EPSS Probability

0.39%

30.8th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Mozilla	Firefox	< 115.34.0
Mozilla	Firefox	< 149.0
Mozilla	Firefox	>= 128.0, < 140.9.0
Mozilla	Thunderbird	< 140.9.0
Mozilla	Thunderbird	< 149.0

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2017643Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-20/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-21/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-22/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-23/Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-24/Vendor Advisory

Timeline

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

Frequently Asked Questions

What is CVE-2026-4692?

Sandbox escape in the Responsive Design Mode component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

How severe is CVE-2026-4692?

CVE-2026-4692 has a CVSS score of 10/10 (CRITICAL severity). The EPSS model estimates a 0.39% probability of exploitation in the next 30 days.

How do I fix CVE-2026-4692?

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-2026-4692?

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

Scan your code now

Source: NVD / NIST