Is CVE-2025-6427 in the CISA KEV catalog?

No. CVE-2025-6427 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2025-6427?

CVE-2025-6427 has a CVSS v3 base score of 9.1 (CRITICAL).

What is the EPSS score for CVE-2025-6427?

CVE-2025-6427 has an EPSS score of 0.30% (22th percentile), estimating the probability of exploitation in the next 30 days.

CVE & CISA-KEV Catalog

CVE-2025-6427

CRITICAL

9.1

CVSS v3

NVD

Description

An attacker was able to bypass the `connect-src` directive of a Content Security Policy by manipulating subdocuments. This would have also hidden the connections from the Network tab in Devtools. This vulnerability was fixed in Firefox 140 and Thunderbird 140.

CWE-693Protection Mechanism Failure

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

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

Exploit Intelligence

0.30%probability of exploitation in 30 days

22ndpercentile

Low risk: more likely to be exploited than 22% of all known CVEs.

References

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-13.