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Microsoft Security Advisory CVE-2019-0820: .NET Core Denial of Service Vulnerability #15

TravisEz13 opened this issue May 21, 2019 · 0 comments


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commented May 21, 2019

Microsoft Security Advisory CVE-2019-0820: .NET Core Denial of Service Vulnerability

Executive Summary

System administrators are advised to update PowerShell Core to an unaffected version (see affected software.)

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET Core 2.1.

A denial of service vulnerability exists when .NET Core improperly process RegEx strings. An attacker who successfully exploited this vulnerability could cause a denial of service against a .NET application.

A remote unauthenticated attacker could exploit this vulnerability by issuing specially crafted requests to a .NET Core application.

The update addresses the vulnerability by correcting how .NET Core applications handle RegEx string processing.


Please use PowerShell/PowerShell#9641 for discussion of this advisory.
Please use dotnet/corefx#37649 for discussion of the .NET aspects this advisory.

Affected Software

The vulnerability affects PowerShell Core prior to the following versions:

PowerShell Core Version Fixed in
6.1 6.1.4
6.2 6.2.1

Advisory FAQ

How do I know if I am affected?

If all of the following are true:

  1. Run pwsh -v, then, check the version in the table in Affected Software to see if your version of PowerShell Core is affected.
  2. If you are running a version of PowerShell Core where the executable is not pwsh or pwsh.exe, then you are affected. This only existed for preview version of 6.0.

How do I update to an unaffected version?

Follow the instructions at Installing PowerShell Core to install the latest version of PowerShell Core.

Other Information

Reporting Security Issues

If you have found a potential security issue in PowerShell Core,
please email details to


You can ask questions about this issue on GitHub in the PowerShell organization.
This is located at
The Announcements repo (
will contain this bulletin as an issue and will include a link to a discussion issue where you can ask questions.

What if the update breaks my script or module?

You can uninstall the newer version of PowerShell Core and install the previous version of PowerShell Core.
This should be treated as a temporary measure.
Therefore, the script or module should be updated to work with the patched version of PowerShell Core.


Microsoft recognizes the efforts of those in the security community who help us protect customers through coordinated vulnerability disclosure.

See acknowledgments for more information.

External Links



V1.0 (May 21, 2019): Advisory published.

Version 1.0
Last Updated 2019-05-21

@PowerShell PowerShell locked and limited conversation to collaborators May 21, 2019

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