CVE-2025-3932: Mozilla Thunderbird

Medium severity, CVSS 6.5. EPSS: 0.4% chance of exploitation in the next 30 days.

It was possible to craft an email that showed a tracking link as an attachment. If the user attempted to open the attachment, Thunderbird automatically accessed the link. The configuration to block remote content did not prevent that. Thunderbird has been fixed to no longer allow access to web pages listed in the X-Mozilla-External-Attachment-URL header of an email. This vulnerability was fixed in Thunderbird 128.10.1 and Thunderbird 138.0.1.

Affected products

• Mozilla Thunderbird: before 128.10.1 (fixed in 128.10.1); from 129.0, before 138.0.1 (fixed in 138.0.1)

Published 2025-05-14. Last modified 2026-06-17.