# CVE-2026-83906: Windows Shell authentication algorithm spoofing

Source: https://junglewise.ai/threats/cve-2026-83906-incorrect-implementation-of-authentication-algorithm-in-windows  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-13. Updated: 2026-10-29  
License: CC BY 4.0 with a link back

CVE-2026-83906 · Severity: medium · CVSS 6.5 · Published 2026-10-13

Windows Shell, which handles user authentication and system operations, contains a flaw in its authentication algorithm that allows an attacker to impersonate legitimate users or systems over a network. An attacker could use this to gain unauthorized access to systems or perform actions as another user without proper credentials.

Technologies: [Microsoft Windows Shell](https://junglewise.ai/threats/technologies/windows-shell), [Microsoft Windows 11 23h2](https://junglewise.ai/threats/technologies/windows-11-23h2), [Microsoft Windows 11 24h2](https://junglewise.ai/threats/technologies/windows-11-24h2), [Microsoft Windows 11 25h2](https://junglewise.ai/threats/technologies/windows-11-25h2), [Microsoft Windows 11 26h1](https://junglewise.ai/threats/technologies/windows-11-26h1), [Microsoft Windows 11 26h2](https://junglewise.ai/threats/technologies/windows-11-26h2), [Microsoft Windows Server 2025](https://junglewise.ai/threats/technologies/windows-server-2025). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-83906 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-83906 being exploited in the wild.

**How severe is CVE-2026-83906?** Medium severity, with a CVSS score of 6.5, published 13 October 2026.

**Which products and versions are affected?** Microsoft Windows Shell.

**Is there a fix for CVE-2026-83906?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-83906 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2026-83906?** Check whether you run Microsoft Windows Shell, Microsoft Windows 11 23h2, Microsoft Windows 11 24h2 or one of the others listed. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability stems from incorrect implementation of an authentication algorithm in Windows Shell, enabling network-based spoofing attacks. An attacker with network access can exploit this flaw to impersonate other users or systems. The vulnerability has not been observed in active exploitation at this time.

## Affected products

- Microsoft Windows Shell

## Timeline

- 2026-10-13: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-83906](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-83906)

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