🔐 CVE Alert

CVE-2025-3522

MEDIUM 6.3

Leak of hashed Window credentials via crafted attachment URL

CVSS Score
6.3
EPSS Score
0.0%
EPSS Percentile
0th

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.

Vendor mozilla
Product thunderbird
Ecosystems
Industries
Technology
Published Apr 15, 2025
Last Updated Apr 13, 2026
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Affected Versions

Mozilla / Thunderbird
All versions affected

References

NVD ↗ CVE.org ↗ EPSS Data ↗
bugzilla.mozilla.org: https://bugzilla.mozilla.org/show_bug.cgi?id=1955372 mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-26/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2025-27/

Credits

Dario Weißer