CVE-2025-6433
CRITICALMozilla Firefox < 140.0 - Improper Certificate Validation
Title source: ruleDescription
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.
Scores
CVSS v3
9.8
EPSS
0.0019
EPSS Percentile
40.6%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
yes
Technical Impact
total
Details
CWE
CWE-295
Status
published
Products (3)
mozilla/firefox
< 140.0
Mozilla/Firefox
140
Mozilla/Thunderbird
140
Published
Jun 24, 2025
Tracked Since
Feb 18, 2026