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CVE-2026-21860

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

Published: Jan 8, 2026Updated: Feb 2, 2026 Sources: CVE List NVD GHSACWE-67
5.3MEDIUM
NVD MITRE
EPSS Score
0.4%
Top 63.7%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
Not available

Description

Werkzeug is a comprehensive WSGI web application library. Prior to version 3.1.5, Werkzeug's safe_join function allows path segments with Windows device names that have file extensions or trailing spaces. On Windows, there are special device names such as CON, AUX, etc that are implicitly present and readable in every directory. Windows still accepts them with any file extension, such as CON.txt, or trailing spaces such as CON. This issue has been patched in version 3.1.5.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:NA:L
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:LAvailability
Low
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Weaknesses

CWE-67

Affected Products

palletsprojects
oss-project·US
werkzeugLibrary
OSS Libraries / pypi
pallets
oss-project·US
werkzeugLibrary
OSS Libraries / pypi
PyPI
package-ecosystem
Werkzeug
OSS Libraries

Exploitability

Official Patch Available

References

https://github.com/pallets/werkzeug/commit/7ae1d254e04a0c33e241ac1cca4783ce6c875ca3
github.com
https://github.com/pallets/werkzeug/security/advisories/GHSA-87hc-h4r5-73f7
github.com
https://nvd.nist.gov/vuln/detail/CVE-2026-21860
nvd.nist.gov
and 1 more references View all →

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