Microsoft Security Advisory CVE-2021-1721: PowerShell Denial of Service Vulnerability
Executive Summary
Microsoft is releasing this security advisory to provide information about a vulnerability in PowerShell 7.1 and 7.0. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.
A denial-of-service vulnerability exists when creating HTTPS web request during X509 certificate chain building.
System administrators are advised to update PowerShell Core to an unaffected version (see affected software.)
Discussion
Please open a support question to discussion the PowerShell aspects of this advisory.
Please use dotnet/runtime#48067 for discussion of the .NET runtime aspects this advisory.
If you have found a potential security issue in PowerShell Core,
please email details to secure@microsoft.com.
Support
You can ask questions about this issue on GitHub in the PowerShell organization.
This is located at https://github.com/PowerShell/.
The Announcements repo (https://github.com/PowerShell/Announcements)
will contain this bulletin as an issue and will include a link to a discussion issue where you can ask questions.
Disclaimer
The information provided in this advisory 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.
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.
Acknowledgments
Microsoft recognizes the efforts of those in the security community who help us protect customers through coordinated vulnerability disclosure.
Microsoft Security Advisory CVE-2021-1721: PowerShell Denial of Service Vulnerability
Executive Summary
Microsoft is releasing this security advisory to provide information about a vulnerability in PowerShell 7.1 and 7.0. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.
A denial-of-service vulnerability exists when creating HTTPS web request during X509 certificate chain building.
System administrators are advised to update PowerShell Core to an unaffected version (see affected software.)
Discussion
Please open a support question to discussion the PowerShell aspects of this advisory. Please use dotnet/runtime#48067 for discussion of the .NET runtime aspects this advisory.
Affected Software
The vulnerability affects PowerShell Core prior to the following versions:
Advisory FAQ
How do I know if I am affected?
If the following is true:
pwsh -v, then, check the version in the table in Affected Software to see if your version of PowerShell Core is affected.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 secure@microsoft.com.
Support
You can ask questions about this issue on GitHub in the PowerShell organization. This is located at https://github.com/PowerShell/. The Announcements repo (https://github.com/PowerShell/Announcements) will contain this bulletin as an issue and will include a link to a discussion issue where you can ask questions.
Disclaimer
The information provided in this advisory 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.
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.
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.
External Links
CVE-2021-1721
Revisions
V1.0 (Feb 11, 2021): Advisory published. v1.1 (March 11, 2021): Updated link for installing PowerShell to an aka.ms link.
Version 1.1 Last Updated 2021-03-11