CVE-2025-6427: firefox — Fix

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.

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CVSS v3.1 Score

9.1

CRITICAL

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

Weakness Type (CWE)

CWE-693 CWE-693

Affected Products

Vendor	Product	Versions
mozilla	firefox	< 140.0

References

Advisories & Patches

https://www.mozilla.org/security/advisories/mfsa2025-51/

Other References

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

Frequently Asked Questions

What is CVE-2025-6427? +

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. It has a CVSS v3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2025-6427? +

CVE-2025-6427 has a CVSS v3.1 score of 9.1 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately.

What products are affected by CVE-2025-6427? +

CVE-2025-6427 affects products from mozilla, specifically: firefox. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-6427? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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