VULNERABILITY INTELLIGENCE

CVE-2025-3522

CVSS score6.3 MEDIUM
EPSS probability0.27%
CISA KEVNot currently listed
Published2025-04-15
Last modified2026-06-17
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L

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.

Weakness classification

  • CWE-601: URL Redirection to Untrusted Site ('Open Redirect')

Primary references