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.

Project Subscriptions

Vendors Products
Mozilla Subscribe
Firefox Subscribe
Advisories
Source ID Title
EUVD EUVD EUVD-2025-21379 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 affects Firefox < 140 and Thunderbird < 140.
Ubuntu USN Ubuntu USN USN-7991-1 Thunderbird vulnerabilities
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Mon, 13 Apr 2026 15:00:00 +0000

Type Values Removed Values Added
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 affects Firefox < 140 and Thunderbird < 140. 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.

Thu, 30 Oct 2025 16:30:00 +0000

Type Values Removed Values Added
Title firefox: connect-src Content Security Policy restriction could be bypassed connect-src Content Security Policy restriction could be bypassed

Tue, 15 Jul 2025 13:45:00 +0000

Type Values Removed Values Added
Metrics epss

{'score': 0.00055}

epss

{'score': 0.00052}


Mon, 14 Jul 2025 18:45:00 +0000

Type Values Removed Values Added
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 affects Firefox < 140. 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 affects Firefox < 140 and Thunderbird < 140.
References

Thu, 03 Jul 2025 17:00:00 +0000

Type Values Removed Values Added
First Time appeared Mozilla
Mozilla firefox
CPEs cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
Vendors & Products Mozilla
Mozilla firefox

Thu, 26 Jun 2025 00:30:00 +0000

Type Values Removed Values Added
Title firefox: connect-src Content Security Policy restriction could be bypassed
References
Metrics threat_severity

None

threat_severity

Moderate


Wed, 25 Jun 2025 15:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-693
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Tue, 24 Jun 2025 12:45:00 +0000

Type Values Removed Values Added
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 affects Firefox < 140.
References

Projects

Sign in to view the affected projects.

cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published:

Updated: 2026-04-13T14:31:00.300Z

Reserved: 2025-06-20T14:51:31.244Z

Link: CVE-2025-6427

cve-icon Vulnrichment

Updated: 2025-06-25T14:21:00.484Z

cve-icon NVD

Status : Modified

Published: 2025-06-24T13:15:23.650

Modified: 2026-04-13T15:17:06.703

Link: CVE-2025-6427

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-06-24T12:28:01Z

Links: CVE-2025-6427 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2025-07-06T22:16:27Z

Weaknesses