CVE-2025-3932: Vulnerability in Mozilla Thunderbird
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.
AI Analysis
Technical Summary
The vulnerability CVE-2025-3932 in Mozilla Thunderbird allowed an attacker to embed a tracking link as an email attachment. When a user opened this attachment, Thunderbird would automatically access the linked web page, ignoring the user's setting to block remote content. This was caused by Thunderbird's handling of the X-Mozilla-External-Attachment-URL email header. The issue was resolved by changes in Thunderbird 128.10.1 and 138.0.1, which block automatic access to URLs specified in this header.
Potential Impact
The impact of this vulnerability is that user privacy could be compromised by automatic access to tracking links without user consent, even if remote content blocking was enabled. This could allow senders to track user interaction with emails. The CVSS score is 6.5 (medium severity), reflecting the potential confidentiality impact without integrity or availability effects. There are no known exploits in the wild at this time.
Mitigation Recommendations
This vulnerability has been fixed in Mozilla Thunderbird versions 128.10.1 and 138.0.1. Users should update to these or later versions to ensure protection. No additional mitigation steps are required as the fix prevents automatic access to URLs in the X-Mozilla-External-Attachment-URL header and respects remote content blocking settings.
CVE-2025-3932: Vulnerability in Mozilla Thunderbird
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.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability CVE-2025-3932 in Mozilla Thunderbird allowed an attacker to embed a tracking link as an email attachment. When a user opened this attachment, Thunderbird would automatically access the linked web page, ignoring the user's setting to block remote content. This was caused by Thunderbird's handling of the X-Mozilla-External-Attachment-URL email header. The issue was resolved by changes in Thunderbird 128.10.1 and 138.0.1, which block automatic access to URLs specified in this header.
Potential Impact
The impact of this vulnerability is that user privacy could be compromised by automatic access to tracking links without user consent, even if remote content blocking was enabled. This could allow senders to track user interaction with emails. The CVSS score is 6.5 (medium severity), reflecting the potential confidentiality impact without integrity or availability effects. There are no known exploits in the wild at this time.
Mitigation Recommendations
This vulnerability has been fixed in Mozilla Thunderbird versions 128.10.1 and 138.0.1. Users should update to these or later versions to ensure protection. No additional mitigation steps are required as the fix prevents automatic access to URLs in the X-Mozilla-External-Attachment-URL header and respects remote content blocking settings.
Technical Details
- Data Version
- 5.1
- Assigner Short Name
- mozilla
- Date Reserved
- 2025-04-25T12:43:02.149Z
- Cisa Enriched
- true
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 682cd0fa1484d88663aec50b
Added to database: 5/20/2025, 6:59:06 PM
Last enriched: 4/14/2026, 11:45:50 AM
Last updated: 5/13/2026, 4:35:41 AM
Views: 105
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