VULNERABILITY

MFSA2025-35 Thunderbird: Security Vulnerabilities fixed in Thunderbird 138.0.1 (CVE-2025-3909)

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MFSA2025-35 Thunderbird: Security Vulnerabilities fixed in Thunderbird 138.0.1 (CVE-2025-3909)

Severity
8
CVSS
(AV:N/AC:M/Au:N/C:P/I:C/A:N)
Published
05/13/2025
Created
05/16/2025
Added
05/15/2025
Modified
06/06/2025

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(s)

  • mozilla-thunderbird-upgrade-138_0_1

References

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