What’s Vulnerable › Vulnerabilities

CVE-2025-3932: Tracking Links in Attachments Bypassed Remote Content Blocking

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-05-14 · updated 2026-06-17
• Weakness: CWE-288

Description

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; from 129.0 before 138.0.1 — fixed in 128.10.1, 138.0.1

How to fix

Upgrade to a fixed version: Mozilla Thunderbird 128.10.1, 138.0.1. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1960412
• https://www.mozilla.org/security/advisories/mfsa2025-34/
• https://www.mozilla.org/security/advisories/mfsa2025-35/
• https://lists.debian.org/debian-lts-announce/2025/05/msg00022.html

Get alerted when CVE-2025-3932 or the next vulnerability affects your stack