CVE-2025-6433 — If a user visited a webpage with an invalid TLS certificate, and granted an exception, the webpage was…

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.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1954033
• https://www.mozilla.org/security/advisories/mfsa2025-51/
• https://www.mozilla.org/security/advisories/mfsa2025-54/