Microsoft Security Advisory CVE-2018-0764: Denial of Service when parsing XML documents

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Microsoft Security Advisory CVE-2018-0764

Denial of Service when parsing XML documents

Executive Summary

Microsoft is releasing this security advisory to provide information about a vulnerability in the open source versions of PowerShell Core. This advisory also provides guidance on what developers can do to update their scripts and module correctly.

Microsoft is aware of a Denial of Service vulnerability in the open source versions of PowerShell Core when improper processing of XML documents by .NET Core occurs. 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 an application using PowerShell to process requests.

The update addresses the vulnerability by correcting how .NET core handles XML document processing.

System administrators are advised to update PowerShell Core to version 6.0.1. This version will also address CVE-2018-0786.

Discussion

Please use PowerShell/PowerShell#6030 for discussion of this advisory.
Please use dotnet/corefx#26237 for discussion of the .NET CoreFx aspects this advisory.

Affected Software

The vulnerability affects PowerShell Core prior to version 6.0.1

Advisory FAQ

How do I know if I am affected?

If all of the following are true:

1. Run pwsh -v (if, you cannot launch PowerShell Core using pwsh you are affected). If the reported version starts with 6.0.0, you are affected.
2. You are using PowerShell to parse XML.

How do I update to an unaffected version?

Follow the instructions at Get PowerShell 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.

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.

External Links

CVE-2018-0764

Revisions

V1.0 (Jan 25, 2018): Advisory published.

Version 1.0
Last Updated 2018-01-25