CVE-2026-4692

moderate-risk

Published 2026-03-24

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.

Do I need to act?

0.03% chance of exploitation

EPSS score — low exploit probability

Not on CISA KEV list

No confirmed active exploitation reported to CISA

Patch status unknown

Check vendor advisories for fix availability and mitigation guidance

CVSS 10.0/10 Critical

NETWORK / LOW complexity

Affected Products (4)

Firefox

Thunderbird

Affected Vendors

Mozilla

References (6)

Permissions Required https://bugzilla.mozilla.org/show_bug.cgi?id=2017643

Vendor Advisory 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/

/ 100

moderate-risk

Severity 33/34 · Critical

Exploitability 0/34 · Minimal

Exposure 10/34 · Low