CVE-2026-4684 Race condition, use-after-free in the Graphics: WebRender component

What is CVE-2026-4684?

CVE-2026-4684 is a high-severity use after free 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

Race condition, use-after-free in the Graphics: WebRender component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

Weakness: CWE-364, CWE-416, CWE-362

Which versions are affected by CVE-2026-4684?

It affects 1 product.

Products include Mozilla Firefox.

How do I fix CVE-2026-4684?

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-2026-4684 being exploited?

There is no known exploitation of CVE-2026-4684 in the wild and no public exploit code.

Other vulnerabilities in Mozilla Firefox

• CVE-2019-11708 Mozilla Firefox and Thunderbird Sandbox Escape Exploited Critical 10.0
• CVE-2010-3765 Mozilla Multiple Products Remote Code Execution Exploited Critical 9.8
• CVE-2022-26486 Mozilla Firefox Use-After-Free Exploited Critical 9.6
• CVE-2022-26485 Mozilla Firefox Use-After-Free Exploited High 8.8
• CVE-2019-11707 Mozilla Firefox and Thunderbird Type Confusion Exploited High 8.8

All Mozilla Firefox vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2026-4684, GHSA-3rrq-fwhx-9wq4, UBUNTU-CVE-2026-4684.