Microsoft has asked system administrators to patch their PowerShell 7 installations against two vulnerabilities that can allow attackers to bypass Windows Defender Application Control (WDAC) to run arbitrary code, and even gain access to plain text credentials.
PowerShell 7 is an open source, cross-platform edition of the command-line shell that helps Windows admins and power users automate a range of administrative tasks with the help of cmdlets.
“To exploit the vulnerability, an attacker needs administrator access on a local machine where PowerShell is running. The attacker could then connect to a PowerShell session and send commands to execute arbitrary code,” says Microsoft to explain the impact of one of the vulnerabilities, tracked as CVE-2020-0951.
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The second flaw, tracked as CVE-2021-41355, is an information disclosure vulnerability in the .NET Core which could be exploited to leak credentials in clear text on devices running non-Windows platforms.
The WDAC mechanism was introduced with Windows 10 to ensure that only trusted apps and drivers can run inside the OS, and block any malicious software or malware.
BleepingComputer explains that by exploiting the WDAC bypass vulnerability in PowerShell 7, threat actors could potentially execute PowerShell commands that would otherwise be flagged as malicious and blocked by WDAC.
The vulnerabilities exist in both PowerShell 7 and the updated PowerShell 7.1 release, and reportedly there isn’t any mitigation to prevent their exploitation.
Microsoft suggests admins to install the updated PowerShell 7.0.8 and 7.1.5 versions, without delay to secure their installations.
“The update addresses the vulnerability by correcting how PowerShell commands are validated when WDAC protection is enabled,” Microsoft assures.
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