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.

Endpoint Security //

Windows

8/13/2018
09:35 AM
Larry Loeb
Larry Loeb
Larry Loeb
50%
50%

Microsoft Cortana Vulnerability Can Unlock a Locked Windows PC

At Black Hat, researchers showed how a vulnerability in Cortana can unlock a locked Windows PC. Microsoft has patched the flaw, but questions remain.

During last week's Black Hat conference in Las Vegas, researchers showed how Microsoft's Cortana virtual assistant could be used to bypass the Windows lock screen. The vulnerability affects Windows 10 machines and Windows 10 Servers.

Amichai Shulman and Tal Be'ery from Kzen Networks, along with Ron Marcovich and Yuval Ron from the Israel Institute of Technology, showed how Cortana's default settings could wreak havoc when abused. The researchers noted that Microsoft has patched this particular problem (CVE-2018-8140) in June, but added there will be other vulnerabilities emerging due to the underlying problem.

Exploiting the vulnerability does not involve any external coder unusual system calls. Code focused defenses such as antivirus, anti-malware and IPS will be blind to such an effort.

(Source: Microsoft)
(Source: Microsoft)

The researchers believe that adding functionality to a locked screen is the root of the situation, and it is dangerous. They conceptualize the lock screen as another desktop with a limited access. That limiting is what reduces the attack surface. Adding additional apps or functionality will only grow that attack surface.

In this case, the lock screen limits the keyboard but allows Cortana to invoke via voice. Once Cortana is active, the lock screen no longer limits the keyboard and Cortana can accept its input.

The researchers found they could then launch local commands without the need for further authentication or user validation. They wrote that they were able to "take over a locked Windows machine and execute arbitrary code. Exploiting the 'Open Sesame' [their moniker for it—ed.]vulnerability attackers can view the contents of sensitive files (text and media), browse arbitrary web sites, download and execute arbitrary executables from the Internet, and under some circumstances gain elevated privileges."

This is a major responsibility shift showing up. The OS used to guarantee the UI was not accessible when the computer was locked. Now, developers need to be aware of the computer's state and not assume a lock will hold.

Mitigating this form of attack is problematic, according to the research report. One method is voice identification. Specifically, that means having Cortana respond to only one speaker. That might stop "evil maid" scenarios -- where someone else tries to access an unattended locked machine -- but will fall to a recorded voice sample of the authorized users saying the opening phrase.


Zero in on the most attractive 5G NR deployment strategies, and take a look ahead to later technology developments and service innovations. Join us for the Deployment Strategies for 5G NR breakfast workshop in LA at MWCA on September 12. Register now to learn from and network with industry experts – communications service providers get in free!

A network-based intercepting proxy, however, has more appeal. It would require that a TLS/SSL certificate be installed on monitored devices. Some organizations already have them installed for web gateway monitoring. Such a tool would monitor all Cortana requests and responses, and could block or modify them.

Until that tool is here, however, the researchers suggest totally disabling Cortana voice in corporate environments. If that is not possible, disabling it on locked screens may help.

This vulnerability shows how an interface change can affect an entire system. More than just secure coding, secure system engineering is required.

Related posts:

— Larry Loeb has written for many of the last century's major "dead tree" computer magazines, having been, among other things, a consulting editor for BYTE magazine and senior editor for the launch of WebWeek.

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
Edge-DRsplash-10-edge-articles
I Smell a RAT! New Cybersecurity Threats for the Crypto Industry
David Trepp, Partner, IT Assurance with accounting and advisory firm BPM LLP,  7/9/2021
News
Attacks on Kaseya Servers Led to Ransomware in Less Than 2 Hours
Robert Lemos, Contributing Writer,  7/7/2021
Commentary
It's in the Game (but It Shouldn't Be)
Tal Memran, Cybersecurity Expert, CYE,  7/9/2021
Register for Dark Reading Newsletters
White Papers
Video
Cartoon
Current Issue
Enterprise Cybersecurity Plans in a Post-Pandemic World
Download the Enterprise Cybersecurity Plans in a Post-Pandemic World report to understand how security leaders are maintaining pace with pandemic-related challenges, and where there is room for improvement.
Flash Poll
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2021-40684
PUBLISHED: 2021-09-22
Talend ESB Runtime in all versions from 5.1 to 7.3.1-R2021-09, 7.2.1-R2021-09, 7.1.1-R2021-09, has an unauthenticated Jolokia HTTP endpoint which allows remote access to the JMX of the runtime container, which would allow an attacker the ability to read or modify the container or software running in...
CVE-2021-37860
PUBLISHED: 2021-09-22
Mattermost 5.38 and earlier fails to sufficiently sanitize clipboard contents, which allows a user-assisted attacker to inject arbitrary web script in product deployments that explicitly disable the default CSP.
CVE-2019-6288
PUBLISHED: 2021-09-22
Edgecore ECS2020 Firmware 1.0.0.0 devices allow Unauthenticated Command Injection via the command1 HTTP header to the /EXCU_SHELL URI.
CVE-2021-41011
PUBLISHED: 2021-09-22
LINE client for iOS before 11.15.0 might expose authentication information for a certain service to external entities under certain conditions. This is usually impossible, but in combination with a server-side bug, attackers could get this information.
CVE-2021-40875
PUBLISHED: 2021-09-22
Improper Access Control in Gurock TestRail versions < 7.2.0.3014 resulted in sensitive information exposure. A threat actor can access the /files.md5 file on the client side of a Gurock TestRail application, disclosing a full list of application files and the corresponding file paths. The corresp...