Content Security Policy Bypass in Firefox by Mozilla
CVE-2025-6427

9.1CRITICAL

Key Information:

Vendor

Mozilla
Status
Firefox
Thunderbird
Vendor
CVE Published:
24 June 2025

What is CVE-2025-6427?

A vulnerability was discovered in Firefox that allows attackers to bypass the connect-src directive of a Content Security Policy through subdocument manipulation. This exploit could obscure the connections made by the attacker in the Network tab of Developer Tools, effectively hiding malicious activities from users and developers. This issue primarily impacts Firefox versions earlier than 140, posing a risk to web applications that rely on CSP for securing their content and resources.

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Affected Version(s)

Firefox < 140

Thunderbird < 140

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/

CVSS V3.1

Score:
9.1
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Alan Li (lebr0nli)
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