CVE-2025-3522: Leak of hashed Window credentials via crafted attachment URL
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Thunderbirdto a version that resolves this vulnerability.Fixed in 137.0.2 - Upgrade
Upgrade
ubuntu/thunderbirdto a version that resolves this vulnerability.Fixed in 1:128.12.0+build1-0ubuntu0.22.04.1 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 128.9.2 - Upgrade
Upgrade
debian/thunderbirdto a version that resolves this vulnerability.Fixed in 1:140.12.0esr-1~deb12u1Fixed in 1:153.6.0esr-1~deb12u2Fixed in 1:140.12.0esr-1~deb13u1Fixed in 1:153.6.0esr-1~deb13u1Fixed in 1:153.5.0esr-1Fixed in 1:153.6.0esr-1 - Upgrade
Upgrade
Thunderbirdto a version that resolves this vulnerability.Fixed in 128.9.2
Event History
Parent advisories
This vulnerability appears in the following advisories.
Peer vulnerabilities
Found alongside the following vulnerabilities.
Frequently Asked Questions
What is the severity of CVE-2025-3522?
CVE-2025-3522 is considered a moderate severity vulnerability due to its potential for exploitation through unvalidated URL handling.
How do I fix CVE-2025-3522?
To fix CVE-2025-3522, update Thunderbird to the latest version beyond 137.0.2.
What versions of Thunderbird are affected by CVE-2025-3522?
CVE-2025-3522 affects Thunderbird versions up to and including 137.0.2 and 128.9.2.
What causes the vulnerability in CVE-2025-3522?
The vulnerability in CVE-2025-3522 is caused by Thunderbird processing the X-Mozilla-External-Attachment-URL header without proper URL validation.
Is user interaction required to exploit CVE-2025-3522?
Yes, user interaction is required to exploit CVE-2025-3522 as the vulnerability is triggered when the user opens an affected email.