CVE-2026-102598

Werkzeug safe_join() allows Windows special device names

Published Sep 29, 2026 CVSS 4.0 · 6.3 Medium EPSS < 1% KEV · Not listed
Description
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

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-g6x2-hccm-hh4m Werkzeug safe_join() allows Windows special device names
History
Type Values Removed Values Added
First Time appeared Palletsprojects
Palletsprojects werkzeug
Vendors & Products Palletsprojects
Palletsprojects werkzeug
Type Values Removed Values Added
Weaknesses CWE-66
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}

threat_severity

Moderate

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description 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.
Title Werkzeug safe_join() allows Windows special device names
Weaknesses CWE-67
References
Metrics cvssV4_0

{'score': 6.3, 'vector': '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Sep 29, 2026, 3:44 PM
Reserved
Sep 29, 2026, 2:18 PM
Status
Awaiting Analysis
Published
Sep 29, 2026, 4:17 PM
Modified
Sep 30, 2026, 7:38 PM
Severity
Moderate
Public date
Sep 29, 2026, 3:16 PM