CVE-2025-6425 The WebCompat WebExtension shipped with Firefox exposed a persistent UUID

What is CVE-2025-6425?

CVE-2025-6425 is a medium-severity vulnerability in Mozilla Firefox, published on 24 Jun 2025. 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

An attacker who enumerated resources from the WebCompat extension could have obtained a persistent UUID that identified the browser, and persisted between containers and normal/private browsing mode, but not profiles. This vulnerability was fixed in Firefox 140, Firefox ESR 115.25, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

Weakness: CWE-200

Which versions are affected by CVE-2025-6425?

It affects 1 product.

Products include Mozilla Firefox.

How do I fix CVE-2025-6425?

Upgrade to a fixed version.

Is CVE-2025-6425 being exploited?

There is no known exploitation of CVE-2025-6425 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-2025-6425, GHSA-2h3c-qrcw-962q, UBUNTU-CVE-2025-6425.