CVE-2025-6427

CRITICAL9.1

connect-src Content Security Policy restriction could be bypassed

Published Jun 24, 2025

Modified 2 months ago

Fix available

Details

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.

Affected Packages

Firefox

Ubuntu 14.04 LTSUbuntu 16.04 LTSUbuntu 18.04 LTSUbuntu 20.04 LTSUbuntu 22.04 LTS

Fixed in:

140

Mozilla Firefox

Windows 10 (1507)Windows 10 (1607) / Server 2016Windows 10 (1809) / Server 2019Windows 10 (1903)Windows 10 (1909)

Fixed in:

140

References

WEBhttps://bugzilla.mozilla.org/show_bug.cgi?id=1966927 ADVISORYhttps://www.cve.org/CVERecord?id=CVE-2025-6427 WEBhttps://www.mozilla.org/security/advisories/mfsa2025-51/WEBhttps://www.mozilla.org/security/advisories/mfsa2025-54/

CVSS Analysis

CVSS v3.1

9.1

Exploitability

Attack Vector

NetworkAV:N

Attack Complexity

LowAC:L

Privileges Required

NonePR:N

User Interaction

NoneUI:N

Scope

UnchangedS:U

Impact

Confidentiality

HighC:H

Integrity

HighI:H

Availability

NoneA:N

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

Ecosystems(28)

Ubuntu 14.04 LTS Ubuntu 16.04 LTS Ubuntu 18.04 LTS Ubuntu 20.04 LTS Ubuntu 22.04 LTS

Timeline

PublishedJun 24, 2025

ModifiedOct 30, 2025