---
id: CVE-2026-102598
title: Werkzeug is a comprehensive WSGI web application library
summary: >-
  Werkzeug is a comprehensive WSGI web application library. Prior to 3.1.9, the
  safe_join function used by send_from_directory can allow a NUL: special-device
  path because safe_join checks the Windows device name without first removing
  an …
severity: medium
cvss: 6.3
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N'
cwe:
  - CWE-67
vendor: pallets
product: werkzeug
affected:
  - werkzeug < 3.1.9
published: '2026-09-29'
updated: '2026-09-29'
sourceUpdated: '2026-09-29T16:17:06.010'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-102598'
references:
  - url: >-
      https://github.com/pallets/werkzeug/commit/8d77320bcdf3a34941ec06dcf16b03c065cd21b6
    label: security-advisories@github.com
  - url: 'https://github.com/pallets/werkzeug/pull/3309'
    label: security-advisories@github.com
  - url: 'https://github.com/pallets/werkzeug/releases/tag/3.1.9'
    label: security-advisories@github.com
  - url: >-
      https://github.com/pallets/werkzeug/security/advisories/GHSA-g6x2-hccm-hh4m
    label: security-advisories@github.com
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-29T15:44:02.973150Z'
cvssSource: cna
ingestedAt: '2026-09-29T16:39:33.263Z'
---

## Overview

Werkzeug is a comprehensive WSGI web application library. Prior to 3.1.9, the safe_join function used by send_from_directory can allow a NUL: special-device path because safe_join checks the Windows device name without first removing an empty NTFS ADS marker. The trigger is that an application runs on Windows with NTFS and serves a user-specified path ending in a special device name such as NUL:. The attack mechanism is that a requested path ends in a Windows special device name with an empty ADS marker. The impact is that the special device opens successfully and the file read hangs indefinitely. This issue is fixed in version 3.1.9.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.