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CVE-2025-3522

6.3 · MEDIUM

Thunderbird processes the X-Mozilla-External-Attachment-URL header to handle attachments which can be hosted externally.

Published Apr 15, 2025CWE-601EPSS 0.27%

Overview

CVE-2025-3522 is a medium-severity vulnerability. It was published on April 15, 2025 and has a CVSS 3.1 base score of 6.3 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 6.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

Thunderbird processes the X-Mozilla-External-Attachment-URL header to handle attachments which can be hosted externally. When an email is opened, Thunderbird accesses the specified URL to determine file size, and navigates to it when the user clicks the attachment. Because the URL is not validated or sanitized, it can reference internal resources like chrome:// or SMB share file:// links, potentially leading to hashed Windows credential leakage and opening the door to more serious security issues. This vulnerability was fixed in Thunderbird 137.0.2 and Thunderbird 128.9.2.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refbugzilla.mozilla.org/show_bug.cgi?id=1955372Refwww.mozilla.org/security/advisories/mfsa2025-26/Refwww.mozilla.org/security/advisories/mfsa2025-27/

How CyberStrike helps

Frequently asked questions

What is CVE-2025-3522?

CVE-2025-3522 is a medium-severity vulnerability. It was published on April 15, 2025 and has a CVSS 3.1 base score of 6.3 (MEDIUM).

How severe is CVE-2025-3522?

This vulnerability has a CVSS 3.1 base score of 6.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2025-3522?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2025-3522?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-3522 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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