CVE-2025-3909 Affecting thunderbird package, versions <1:128.10.1esr-1


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.04% (12th percentile)

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • Snyk IDSNYK-DEBIANUNSTABLE-THUNDERBIRD-10168043
  • published15 May 2025
  • disclosed14 May 2025

Introduced: 14 May 2025

NewCVE-2025-3909  (opens in a new tab)

How to fix?

Upgrade Debian:unstable thunderbird to version 1:128.10.1esr-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 Debian. See How to fix? for Debian:unstable 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