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CVE-2025-6427

Mozilla Firefox vulnerability

9.1 CRITICALEPSS 0.37%
  1. Published24 Jun 2025

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

Mozilla Firefox< 140.0

Remediation

Fixed in
Mozilla Firefox≥ 140.0

References

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Frequently asked

Is CVE-2025-6427 being actively exploited?

CVE-2025-6427 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.37%.

How severe is CVE-2025-6427?

CVE-2025-6427 has a CVSS 3.1 base score of 9.1, rated critical. EPSS estimates a 0.37% probability of exploitation.

Which products are affected by CVE-2025-6427?

Affected products include Mozilla Firefox.

How do I fix CVE-2025-6427?

Upgrade affected software to a fixed version, for example Mozilla Firefox 140.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2025-6427 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.