CVE-2025-6427

connect-src Content Security Policy restriction could be bypassed

State: Published
Severity: 9.1 Critical
Published: Jun 24, 2025
Updated: Apr 13, 2026
Reserved: Jun 20, 2025

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.

Scores

CVSS	Score	Vector	Source
3.1	9.1 Critical	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N	CISA-ADP

Weaknesses

CWE-693 Protection Mechanism Failure

Affected Products

Product	Versions
FirefoxMozilla	140 and laterNot affected
ThunderbirdMozilla	140 and laterNot affected

References

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

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