CVE-2026-4689 Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component
An integer overflow in the XPCOM component allows sandbox escape, enabling code execution and privilege escalation in Firefox and Thunderbird.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-4689?
CVE-2026-4689 is a critical vulnerability in Mozilla Firefox, published on 24 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Which versions are affected by CVE-2026-4689?
It affects 2 products.
Products include Mozilla Firefox, Mozilla Thunderbird.
How do I fix CVE-2026-4689?
Upgrade to a fixed version.
Is CVE-2026-4689 being exploited?
There is no known exploitation of CVE-2026-4689 in the wild and no public exploit code.
Other vulnerabilities in Mozilla Firefox
Sources
Also known as DEBIAN-CVE-2026-4689, GHSA-j5qx-hh9g-j6wj, UBUNTU-CVE-2026-4689.