CVE-2026-4696 Use-after-free in the Layout: Text and Fonts component

Critical 9.8 Published 24 Mar 2026 Updated 15 Jul 2026

A use-after-free flaw in the text and fonts layout engine allows attackers to execute arbitrary code via malicious web content.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-4696?

CVE-2026-4696 is a critical use after free 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

Use-after-free in the Layout: Text and Fonts component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

Weakness: CWE-825, CWE-416

Which versions are affected by CVE-2026-4696?

It affects 1 product.

Products include Mozilla Firefox.

How do I fix CVE-2026-4696?

Upgrade to a fixed version.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2026-4696 being exploited?

There is no known exploitation of CVE-2026-4696 in the wild and no public exploit code.

All Mozilla Firefox vulnerabilities

Sources

Also known as DEBIAN-CVE-2026-4696, GHSA-h22r-8qx2-2mv3, UBUNTU-CVE-2026-4696.