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Test your applicationsUpgrade RHEL:10 thunderbird-debuginfo to version 0:128.10.0-1.el10_0 or higher.
This issue was patched in RHSA-2025:7507.
Note: Versions mentioned in the description apply only to the upstream thunderbird-debuginfo package and not the thunderbird-debuginfo package as distributed by RHEL.
See How to fix? for RHEL:10 relevant fixed versions and status.
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.