CVE-2025-6433

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.

CVSS v3.1 Score

9.8

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Weakness Type (CWE)

CWE-295 CWE-295

Affected Products

Vendor	Product	Versions
mozilla	firefox	< 140.0

References

Advisories & Patches

https://www.mozilla.org/security/advisories/mfsa2025-51/

Other References

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

Frequently Asked Questions

What is CVE-2025-6433? +

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. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2025-6433? +

CVE-2025-6433 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately.

What products are affected by CVE-2025-6433? +

CVE-2025-6433 affects products from mozilla, specifically: firefox. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-6433? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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