9.8

CVE-2025-6433: mozilla firefox Improper Certificate Validation

CVSS: 9.8v3.1CriticalModified
AliasesUBUNTU-CVE-2025-6433CGA-3p5m-x9xx-qrmpCGA-fhw4-g947-69gg
Published 24-06-2025Last modified 13-04-2026
Open JSON

Vulnerability summary

CVE-2025-6433 is a critical (CVSS 9.8) Improper Certificate Validation vulnerability in mozilla firefox. EPSS estimates a 0.30% chance of exploitation in the next 30 days, higher than 21.1% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.8/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.30%
0%100%
Low · +0.02 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 6 · Related 8
OPENSUSE-SU-2025:15325-1OPENSUSE-SU-2025:15371-1OPENSUSE-SU-2025:15383-1SUSE-SU-2025:02339-1SUSE-SU-2025:02529-1SUSE-SU-2025:02546-1

Timeline

  1. 24-06-2025
    PublishedVulnerability first disclosed.
  2. 13-04-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.30%

Chance of exploitation in the next 30 days

Percentile

21%

Versus all other CVEs

30-day change

+0.02 pp

From 0.28% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.30%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Ubuntu8 products
  • mozjs102All versions (No fix recorded)
  • mozjs115All versions (No fix recorded)
  • mozjs38All versions (No fix recorded)
  • mozjs52All versions (No fix recorded)
  • mozjs68All versions (No fix recorded)
Chainguard2 products
  • firefox< 140-r0
  • firefox-esr< 140-r0
Mozilla1 product
Wolfi1 product
  • firefox< 140-r0

4 vendors · 12 products

References

7 links