🔐 CVE Alert

CVE-2025-6433

CRITICAL 9.8

WebAuthn would allow a user to sign a challenge on a webpage with an invalid TLS certificate

CVSS Score
9.8
EPSS Score
0.0%
EPSS Percentile
0th

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.

Vendor mozilla
Product firefox
Ecosystems
Industries
Technology
Published Jun 24, 2025
Last Updated Apr 13, 2026
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Affected Versions

Mozilla / Firefox
All versions affected
Mozilla / Thunderbird
All versions affected

References

NVD ↗ CVE.org ↗ EPSS Data ↗
bugzilla.mozilla.org: https://bugzilla.mozilla.org/show_bug.cgi?id=1954033 mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-51/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-54/

Credits

Simon