CVE-2026-4692 Sandbox escape in the Responsive Design Mode component
An attacker can escape the sandbox in Responsive Design Mode to execute arbitrary code, affecting Firefox and Thunderbird users.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-4692?
CVE-2026-4692 is a critical vulnerability in Mozilla Firefox, published on 24 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-653
Which versions are affected by CVE-2026-4692?
It affects 2 products.
Products include Mozilla Firefox, Mozilla Thunderbird.
How do I fix CVE-2026-4692?
Upgrade to a fixed version.
Is CVE-2026-4692 being exploited?
There is no known exploitation of CVE-2026-4692 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Other vulnerabilities in Mozilla Firefox
Sources
Also known as DEBIAN-CVE-2026-4692, GHSA-cm3f-xp4p-xgj7, UBUNTU-CVE-2026-4692.