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CVE-2025-6433

Critical

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.

SeverityCritical
CVSS9.8
Exploit probability—
ProductMozilla Firefox
PublishedJun 24, 2025
First seenJun 24, 2025
Weakness typeCWE-295CWE-295

How to fix

Update
  • mozilla firefox140.0 or later

Affected products

ProductAffected versionsFixed in
mozilla firefoxv < 140.0140.0

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