vulnerability
Ubuntu: USN-7663-1 (CVE-2025-3909): Thunderbird vulnerabilities
| Severity | CVSS | Published | Added | Modified |
|---|---|---|---|---|
| 6 | (AV:N/AC:L/Au:N/C:P/I:P/A:N) | May 14, 2025 | Jul 23, 2025 | Aug 18, 2025 |
Description
Thunderbird's handling of the X-Mozilla-External-Attachment-URL header can be exploited to execute JavaScript in the file:/// context. By crafting a nested email attachment (message/rfc822) and setting its content type to application/pdf, Thunderbird may incorrectly render it as HTML when opened, allowing the embedded JavaScript to run without requiring a file download. This behavior relies on Thunderbird auto-saving the attachment to /tmp and linking to it via the file:/// protocol, potentially enabling JavaScript execution as part of the HTML. This vulnerability affects Thunderbird < 128.10.1 and Thunderbird < 138.0.1.
Solution
References
- CVE-2025-3909
- https://attackerkb.com/topics/CVE-2025-3909
- CWE-290
- UBUNTU-USN-7663-1
- URL-https://bugzilla.mozilla.org/show_bug.cgi?id=1958376
- URL-https://ubuntu.com/security/notices/USN-7663-1
- URL-https://www.cve.org/CVERecord?id=CVE-2025-3909
- URL-https://www.mozilla.org/en-US/security/advisories/mfsa2025-34/#CVE-2025-3909
- URL-https://www.mozilla.org/security/advisories/mfsa2025-34/
- URL-https://www.mozilla.org/security/advisories/mfsa2025-35/
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