by Kastro
Paper/Archive/CVE-2025-6433

CVE-2025-6433

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

EPSS 0.3%CVSS 9.8
critical.is priorityof 100
34
CVSS 9.8 (ADP)9.8 / 10 × 3029.4Not in CISA KEV+300.0EPSS percentile 22.5.225 × 204.5No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
Firefoxsee advisory140CNA
Thunderbirdsee advisory140CNA

Scores by source

CISA ADP9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: total

References

refbugzilla.mozilla.org/show_bug.cgi?id=1954033refmozilla.org/security/advisories/mfsa2025-51refmozilla.org/security/advisories/mfsa2025-54