CVE-2025-6427

CRITICAL

Firefox < 140.0 - Content Security Policy Bypass via Subdocument Manipulation

Title source: llm
STIX 2.1

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.

References (3)

Core 3

Scores

CVSS v3 9.1
EPSS 0.0030
EPSS Percentile 21.6%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CISA SSVC

Vulnrichment
Exploitation none
Automatable yes
Technical Impact total

Details

CWE
CWE-693
Status published
Products (3)
mozilla/firefox < 140.0
Mozilla/Firefox 140
Mozilla/Thunderbird 140
Published Jun 24, 2025
Tracked Since Feb 18, 2026