CVE-2025-3909

Publication date 14 May 2025

Last updated 22 July 2025


Ubuntu priority

Cvss 3 Severity Score

6.5 · Medium

Score breakdown

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.

Status

Package Ubuntu Release Status
thunderbird 25.04 plucky
Not affected
24.10 oracular Ignored end of life, was needs-triage
24.04 LTS noble
Not affected
22.04 LTS jammy
Fixed 1:128.12.0+build1-0ubuntu0.22.04.1
20.04 LTS focal Not in release

Severity score breakdown

Parameter Value
Base score 6.5 · Medium
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Scope Unchanged
Confidentiality Low
Integrity impact Low
Availability impact None
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N