CVE-2025-6433 | WebAuthn would allow a user to sign a challenge on a webpage with an invalid TLS certificate

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.

Published: 2025-06-24 Last update: 2026-04-13 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-6433 is rated Moderate Risk (53.6/100): CVSS Critical severity, with low exploitation likelihood (EPSS 0.19%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-6433

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-04-20 0.06% 0.19% +0.13%
2 2026-03-10 0.01% 0.06% +0.05%
3 2025-06-25 — 0.01% —

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-6433

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2025-6433

OS Trackers for CVE-2025-6433

vendor priority summary link
alpine — CVE-2025-6433: 1 source package rows (firefox); 148 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 148. https://security.alpinelinux.org/vuln/CVE-2025-6433
debian not yet assigned CVE-2025-6433 not yet assigned priority: Debian including 1 source packages (firefox), 1 status rows across 1 suites (sid): resolved 1. https://security-tracker.debian.org/tracker/CVE-2025-6433
redhat low — https://access.redhat.com/security/cve/CVE-2025-6433
suse high CVE-2025-6433 severity important: SUSE including 68 source package names (MozillaFirefox-140.0-112.270.2, MozillaFirefox-140.0.2-1.1, …), 340 product×package rows across 42 product lines (Image SLES12-SP5-SAP-Azure-LI-BYOS-Production, Image SLES12-SP5-SAP-Azure-VLI-BYOS-Production, … (42 product lines)): Fixed 340. https://www.suse.com/security/cve/CVE-2025-6433/
ubuntu medium CVE-2025-6433 medium priority: Ubuntu including 9 source packages (firefox, mozjs102, …), 58 status rows across 8 suites (bionic, focal, jammy, noble, oracular, plucky, questing, upstream): DNE 28, ignored 10, needs-triage 9, not-affected 9, released 2. https://ubuntu.com/security/CVE-2025-6433

Affected software / configurations for CVE-2025-6433

Vendor Product Version Raw CPE
mozilla firefox < 140.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*

References for CVE-2025-6433

cvelogic Threat Intelligence