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CVE-2026-102598

Werkzeug safe_join() allows Windows special device names

MEDIUM
6.3
CVSS Score
Published: September 29, 2026 at 03:16 PM UTC
Updated: September 30, 2026 at 07:38 PM UTC
1 product affected across 1 vendorWerkzeug

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Severity
MEDIUM6.3
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Werkzeug· Pallets
60%
v < 3.1.9
Affected range stops below 3.1.9, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (4)

x_refsource_CONFIRM
Source: cverecord
https://github.com/pallets/werkzeug/security/advisories/GHSA-g6x2-hccm-hh4m
x_refsource_MISC
Source: cverecord
https://github.com/pallets/werkzeug/pull/3309
x_refsource_MISC
Source: cverecord
https://github.com/pallets/werkzeug/commit/8d77320bcdf3a34941ec06dcf16b03c065cd21b6
x_refsource_MISC
Source: cverecord
https://github.com/pallets/werkzeug/releases/tag/3.1.9

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.3MEDIUMGitHub_M
Vector?

Quick Info

StatusAWAITING ANALYSIS
CWE
CWE-67

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