Microsoft Security Bulletin MS16-021 - Important

Security Update for NPS RADIUS Server to Address Denial of Service (3133043)

Published: February 9, 2016

Version: 1.0

Executive Summary

This security update resolves a vulnerability in Microsoft Windows. The vulnerability could cause denial of service on a Network Policy Server (NPS) if an attacker sends specially crafted username strings to the NPS, which could prevent RADIUS authentication on the NPS.

This security update is rated Important for all supported editions of Windows Server 2008 (excluding Itanium), and Windows Server 2008 R2 (excluding Itanium), and all supported editions of Windows Server 2012 and Windows Server 2012 R2. For more information, see the Affected Software section.

The security update addresses the vulnerability by changing how NPS parses username queries when implementing RADIUS. For more information about the vulnerability, see the Vulnerability Information section.

For more information about this update, see Microsoft Knowledge Base Article 3133043.

Affected Software and Vulnerability Severity Ratings

The following software versions or editions are affected. Versions or editions that are not listed are either past their support life cycle or are not affected. To determine the support life cycle for your software version or edition, see Microsoft Support Lifecycle.

The severity ratings indicated for each affected software assume the potential maximum impact of the vulnerability. For information regarding the likelihood, within 30 days of this security bulletin’s release, of the exploitability of the vulnerability in relation to its severity rating and security impact, please see the Exploitability Index in the February bulletin summary.

*The Updates Replaced column shows only the latest update in any chain of superseded updates. For a comprehensive list of updates replaced, go to the Microsoft Update Catalog, search for the update KB number, and then view update details (updates replaced information is provided on the Package Details tab).

Vulnerability Information

Network Policy Server RADIUS Implementation Denial of Service Vulnerability - CVE-2016-0050

A denial of service vulnerability exists when a Network Policy Server (NPS) improperly handles a Remote Authentication Dial-In User Service (RADIUS) authentication request. An unauthenticated attacker who successfully exploited this vulnerability could send specially crafted username strings to a Network Policy Server (NPS) causing a denial of service condition for RADIUS authentication on the NPS.

Note that the denial of service vulnerability would not allow an attacker to execute code or to elevate user rights. To exploit the vulnerability, an attacker would need to have network access to the affected NPS and then create an application to send specially crafted RADIUS authentication requests to the NPS.

The security update addresses the vulnerability by changing how the NPS parses username queries when implementing RADIUS.

The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Mitigating Factors

Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds

Microsoft has not identified any workarounds for this vulnerability.

Security Update Deployment

For Security Update Deployment information, see the Microsoft Knowledge Base article referenced in the Executive Summary.

Acknowledgments

Microsoft recognizes the efforts of those in the security community who help us protect customers through coordinated vulnerability disclosure. See Acknowledgments for more information.

Disclaimer

The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

Revisions

• V1.0 (February 9, 2016): Bulletin published.

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