Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Application Security

12/4/2019
11:00 AM
Kelly Sheridan
Kelly Sheridan
Quick Hits
Connect Directly
Twitter
LinkedIn
Google+
RSS
E-Mail
50%
50%

Microsoft Issues Advisory for Windows Hello for Business

An issue exists in Windows Hello for Business when public keys persist after a device is removed from Active Directory, if the AD exists, Microsoft reports.

Microsoft has issued an advisory (ADV190026) to provide guidance to businesses following the disclosure of an issue in Windows Hello for Business (WHfB). The problem exists when public keys persist following a device's removal from Active Directory, if the Active Directory exists.

The issue was discovered by Michael Grafnetter, IT security researcher and trainer for CQURE and GOPAS, who has been investigating the inner workings of WHfB and discovered multiple attack vectors for the passwordless authentication tool. One of these vectors involves msDS-KeyCredentialLink, which could potentially be used or misused for persistence by an attacker.

Today's advisory refers to another one of his findings. When someone sets up WHfB, the WHfB public key is written to the on-premises AD, and its keys are tied to a user and device that has been added to Azure AD. If the device is removed, its linked WHfB key is considered orphaned. However, these orphaned keys are not deleted, even if their corresponding device is removed. While any authentication to Azure AD using an orphaned key will be rejected, some of these WHfB keys cause a security issue in AD 2016 and 2019 in hybrid or on-premises environments.

An authenticated attacker could access orphaned keys created on Trusted Platform Modules (TPMs) affected by CVE-2017-15361, as detailed in separate security advisory ADV170012, to compute their WHfB private key using the orphaned public keys. The attacker could use the stolen private key to authenticate as the user within the domain with Public Key Cryptography for Initial Authentication (PKINIT).

"This attack is possible even if firmware and software updates have been applied to TPMs that were affected by CVE-2017-15361 because the corresponding public keys might still exist in Active Directory," Microsoft explains in its advisory. Its advisory is intended to provide guidance to clean up orphaned public keys created using an unpatched TPM, before the updates detailed in ADV170012 were applied.

So far, there is no evidence to suggest this issue has been used to attack machines in the wild, officials say. Read mitigation steps in Microsoft's full advisory here.

Check out The Edge, Dark Reading's new section for features, threat data, and in-depth perspectives. Today's top story: "A Cause You Care About Needs Your Cybersecurity Help."

Kelly Sheridan is the Staff Editor at Dark Reading, where she focuses on cybersecurity news and analysis. She is a business technology journalist who previously reported for InformationWeek, where she covered Microsoft, and Insurance & Technology, where she covered financial ... View Full Bio

Comment  | 
Print  | 
More Insights
Comments
Threaded  |  Newest First  |  Oldest First
Cybersecurity Industry: It's Time to Stop the Victim Blame Game
Jessica Smith, Senior Vice President, The Crypsis Group,  2/25/2020
5 Ways to Up Your Threat Management Game
Wayne Reynolds, Advisory CISO, Kudelski Security,  2/26/2020
Google Adds More Security Features Via Chronicle Division
Robert Lemos, Contributing Writer,  2/25/2020
Register for Dark Reading Newsletters
White Papers
Video
Cartoon
Current Issue
6 Emerging Cyber Threats That Enterprises Face in 2020
This Tech Digest gives an in-depth look at six emerging cyber threats that enterprises could face in 2020. Download your copy today!
Flash Poll
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2020-9447
PUBLISHED: 2020-02-28
The file-upload feature in GwtUpload 1.0.3 allows XSS via a crafted filename.
CVE-2019-10064
PUBLISHED: 2020-02-28
hostapd before 2.6, in EAP mode, makes calls to the rand() and random() standard library functions without any preceding srand() or srandom() call, which results in inappropriate use of deterministic values. This was fixed in conjunction with CVE-2016-10743.
CVE-2019-8741
PUBLISHED: 2020-02-28
A denial of service issue was addressed with improved input validation.
CVE-2020-9399
PUBLISHED: 2020-02-28
The Avast AV parsing engine allows virus-detection bypass via a crafted ZIP archive. This affects versions before 12 definitions 200114-0 of Antivirus Pro, Antivirus Pro Plus, and Antivirus for Linux.
CVE-2020-9442
PUBLISHED: 2020-02-28
OpenVPN Connect 3.1.0.361 on Windows has Insecure Permissions for %PROGRAMDATA%\OpenVPN Connect\drivers\tap\amd64\win10, which allows local users to gain privileges by copying a malicious drvstore.dll there.