#VU107463 Information disclosure in Mozilla Thunderbird - CVE-2025-3522

Vulnerability identifier: #VU107463

Vulnerability risk: Medium

CVSSv4.0: 1.2 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2025-3522

CWE-ID: CWE-200

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Mozilla Thunderbird
Client/Desktop applications / Messaging software

Vendor: Mozilla

Description

The vulnerability allows a remote attacker to gain access to potentially sensitive information.

The vulnerability exists due to a missing URL validation when processing the X-Mozilla-External-Attachment-URL header to handle externally hosted attachments. A remote attacker can send a specially crafted email to the victim that contains a link with an internally referenced document, such as "chrome://" or "chrome://" and force Thunderbird to share hashed Windows credentials with that URL, leading to information disclosure.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Mozilla Thunderbird: 128.0 - 128.9.1, 130.0 - 137.0.1

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External links
https://www.mozilla.org/en-US/security/advisories/mfsa2025-27/
https://www.mozilla.org/en-US/security/advisories/mfsa2025-26/
https://bugzilla.mozilla.org/show_bug.cgi?id=1955372

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.