CVE-2025-6427CRITICAL 9.1EPSS p21.7%

CVE-2025-6427CVE-2025-6427

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.

Scoring

CVSS 3.19.1 (CRITICAL)
VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS0.30% probability of exploitation · percentile 21.7% · 2026-06-19T12:03:05Z
Published2025-06-24
Last modified2026-04-13

Underlying weaknesses· 1

CWE-693

References

  1. https://bugzilla.mozilla.org/show_bug.cgi?id=1966927
  2. https://www.mozilla.org/security/advisories/mfsa2025-51/
  3. https://www.mozilla.org/security/advisories/mfsa2025-54/

1

TypeTargetConfidenceTier
WeaknessProtection Mechanism Failurecwe-6930%live

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Sourced from NVD + FIRST.org EPSS. Curated for EU compliance use cases by Adam Lundqvist, Founder at SQUR.