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CVE-2025-6433

26
FAUCET Score

CVE-2025-6433 describes a critical vulnerability in Firefox and Thunderbird versions prior to 140, where a webpage with an invalid TLS certificate could still prompt a user for WebAuthn authentication if an exception was granted, violating security specifications. This vulnerability carries a CVSS score of 9.8 (CRITICAL) due to its network-based attack vector, low attack complexity, and high potential for confidentiality, integrity, and availability impacts. While no active exploits, public exploit code, or significant community discussion have been observed, the high FAUCET Risk Score of 87/100 indicates a serious potential threat.

Impacted Technologies

VendorProductVersion(s)CPE
< 140.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.24%
Probability of exploitation in next 30 days
EPSS Percentile
15.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0024 is in the 1st percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (1)

mozillavendor investigatingvia nvd_reference
View patch

Vendor Advisories (1)

redhatCVE-2025-6433Low

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

Jun 24, 2025

References

bugzilla.mozilla.org / show_bug.cgi
Permissions Required
mozilla.org / security/advisories/mfsa2025-51
Vendor Advisory
mozilla.org / security/advisories/mfsa2025-54