CVE-2025-6433 WebAuthn would allow a user to sign a challenge on a webpage with an invalid TLS certificate

What is CVE-2025-6433?

CVE-2025-6433 is a critical vulnerability in Mozilla Firefox, published on 24 Jun 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

If a user visited a webpage with an invalid TLS certificate, and granted an exception, the webpage was able to provide a WebAuthn challenge that the user would be prompted to complete. This is in violation of the WebAuthN spec which requires "a secure transport established without errors". This vulnerability was fixed in Firefox 140 and Thunderbird 140.

Weakness: CWE-295

Which versions are affected by CVE-2025-6433?

It affects 1 product.

Products include Mozilla Firefox.

How do I fix CVE-2025-6433?

Upgrade to a fixed version.

Is CVE-2025-6433 being exploited?

There is no known exploitation of CVE-2025-6433 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 GHSA-7f3m-mqm5-5x2c, UBUNTU-CVE-2025-6433.