CVE-2026-21860: Werkzeug safe_join() allows Windows special device names with compound extensions

Overview

Severity

Medium (CVSS 5.3)

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Exploit Status

Not Exploited

Patch Tuesday

2026-Jan

Released

2026-01-11

Last Updated

2026-02-21

EPSS Score

0.02% (percentile: 6.1%)

Affected Products (6)

Open Source Software

• cbl2 python-tensorboard 2.11.0-3 on CBL Mariner 2.0
• azl3 python-tensorboard 2.16.2-6 on Azure Linux 3.0

Other

• 19837-17086
• 20827-17084
• 17600-17084

Mariner

• azl3 tensorflow 2.16.1-9 on Azure Linux 3.0

Revision History

• 2026-01-11: Information published.
• 2026-01-12: Information published.
• 2026-01-13: Information published.
• 2026-02-21: Information published.