CVE-2026-21860: PYSEC-2026-2044 - Werkzeug safe_join() allows Windows special device names with compound extensions

CVE-2026-21860 · Severity: low · CVSS 3.1 · Published 2026-07-07

Werkzeug safe_join() allows Windows special device names with compound extensions

Technologies: werkzeug (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-21860 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-21860 being exploited in the wild.
How severe is CVE-2026-21860?
Low severity, with a CVSS score of 3.1, published 7 July 2026.
Which products and versions are affected?
werkzeug (PyPI) ECOSYSTEM:introduced=0,fixed=3.1.5.
Is there a fix for CVE-2026-21860?
Yes. werkzeug (PyPI): upgrade to 3.1.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2026-21860?
Check whether you run werkzeug (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • werkzeug (PyPI): upgrade to 3.1.5 or later
    pip install "werkzeug>=3.1.5"

Affected products

  • werkzeug (PyPI) ECOSYSTEM:introduced=0,fixed=3.1.5

Identifiers

  • CVE-2026-21860
  • GHSA-87hc-h4r5-73f7
  • PYSEC-2026-2044

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.