CVE-2026-109722 JIT miscompilation in the JavaScript Engine: JIT component
A JIT miscompilation flaw in the JavaScript engine allows attackers to execute arbitrary code, requiring users to update Firefox and Thunderbird.
- 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-2026-109722?
CVE-2026-109722 is a high-severity code injection vulnerability in Mozilla Firefox, published on 13 Oct 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
JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 158, Firefox ESR 115.43, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
Weakness: CWE-670
Which versions are affected by CVE-2026-109722?
How do I fix CVE-2026-109722?
Upgrade to a fixed version.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-109722 being exploited?
There is no known exploitation of CVE-2026-109722 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as DEBIAN-CVE-2026-109722, GHSA-595g-xpmf-vrxq, UBUNTU-CVE-2026-109722.