Bug 2543241 (CVE-2026-102598)

Summary:	CVE-2026-102598 werkzeug: werkzeug: Denial of Service via safe_join() Windows special device paths
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	Keywords:	Security
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Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in werkzeug. A remote attacker can cause a Denial of Service (DoS) when an application runs on Windows systems using the NTFS file system. By supplying a file path containing a reserved Windows device name with an Alternate Data Stream (ADS) marker, an attacker can bypass path sanitization in safe_join(). This causes the server to hang indefinitely while attempting to read the special device, making the service unavailable to users.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
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Description OSIDB Bzimport 2026-09-29 15:35:25 UTC

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.