CVE-2026-8962 Mitigation bypass in the DOM: Security component

High 8.1 Published 19 May 2026 Updated 20 May 2026

An attacker can bypass DOM security mitigations in Firefox and Thunderbird, potentially enabling further exploitation of the browser environment.

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-2026-8962?

CVE-2026-8962 is a high-severity vulnerability in Mozilla Firefox, published on 19 May 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

Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

Weakness: CWE-693

Which versions are affected by CVE-2026-8962?

It affects 2 products.

Products include Mozilla Firefox, Mozilla Thunderbird.

How do I fix CVE-2026-8962?

Upgrade to a fixed version.

Is CVE-2026-8962 being exploited?

There is no known exploitation of CVE-2026-8962 in the wild and no public exploit code.

All Mozilla Firefox vulnerabilities

Sources

Also known as DEBIAN-CVE-2026-8962, GHSA-93x2-246x-h3jh, UBUNTU-CVE-2026-8962.