CVE-2025-6433

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

CVSS 9.8 CRITICALEPSS 0.2%CWE-295

Vexday Risk Score

28Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 9.8EPSS 0.2%KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

24 Jun 2025Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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

Affected products

Mozilla · Firefox Mozilla · Thunderbird

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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/