CVE-2025-3909 Affecting thunderbird package, versions <1:128.12.0+build1-0ubuntu0.22.04.1


Severity

Recommended
medium

Based on Ubuntu security rating.

Threat Intelligence

EPSS
0.08% (25th percentile)

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  • Snyk IDSNYK-UBUNTU2204-THUNDERBIRD-10285368
  • published23 Jul 2025
  • disclosed14 May 2025

Introduced: 14 May 2025

CVE-2025-3909  (opens in a new tab)

How to fix?

Upgrade Ubuntu:22.04 thunderbird to version 1:128.12.0+build1-0ubuntu0.22.04.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream thunderbird package and not the thunderbird package as distributed by Ubuntu. See How to fix? for Ubuntu:22.04 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1