CVE-2026-83906

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Windows Shell Authentication Algorithm Spoofing

Publication date: 2026-10-13

Last updated on: 2026-10-13

Assigner: Microsoft Corporation

Description

Incorrect implementation of authentication algorithm in Windows Shell allows an unauthorized attacker to perform spoofing over a network.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-10-13

Last Modified

2026-10-13

Generated

2026-10-19

AI Q&A

2026-10-14

EPSS Evaluated

2026-10-18

NVD

CVE-2026-83906

EUVD

EUVD-2026-99431

Affected Vendors & Products

Vendor	Product	Version / Range
Microsoft	Windows	11 version 23H2 10.0.22631.0
Microsoft	Windows	11 Version 23H2 10.0.22631.0
Microsoft	Windows	11 Version 24H2 10.0.26100.0
Microsoft	Windows	11 Version 25H2 10.0.26200.0
Microsoft	Windows	11 version 26H1 10.0.28000.0
Microsoft	Windows	11 Version 26H2 10.0.26300.0
Microsoft	Windows	Server 2025 10.0.26100.0
Microsoft	Windows	Server 2025 (Server Core installation) 10.0.26100.0

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-303	The requirements for the product dictate the use of an established authentication algorithm, but the implementation of the algorithm is incorrect.

Attack-Flow Graph

Executive Summary

This vulnerability involves an incorrect implementation of an authentication algorithm in Windows Shell. It allows an unauthorized attacker to perform spoofing over a network, potentially tricking systems into accepting malicious input as legitimate.

Impact Analysis

An attacker could exploit this to impersonate legitimate users or systems, leading to unauthorized access, data breaches, or further network compromise. Users of affected Windows versions may be at risk if the vulnerability is not patched.

Compliance Impact

This vulnerability enables spoofing attacks due to incorrect authentication implementation, which could allow unauthorized access or impersonation. Such attacks may lead to unauthorized data exposure or manipulation, potentially violating GDPR's integrity and confidentiality requirements or HIPAA's access controls for protected health information.

Mitigation Strategies

Apply the latest security updates from Microsoft to address the authentication algorithm implementation issue in Windows Shell. Monitor the Microsoft Update Guide for patches specific to CVE-2026-83906.

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