Microsoft Security Advisory CVE-2019-1301: Denial of Service Vulnerability in PowerShell Core

Executive Summary

A denial of service vulnerability exists when PowerShell Core or .NET Core improperly handles web requests. An attacker who successfully exploited this vulnerability could cause a denial of service against a PowerShell Core scripts.

The update addresses the vulnerability by correcting how the .NET Core handles web requests.

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/announcements#121 for discussion of the .NET aspects this advisory.

<a name="affected-software">Affected Software</a>

The vulnerability affects PowerShell Core prior to the following versions:

| PowerShell Core Version | Fixed in | |-------------------------|-------------------| | 6.1 | 6.1.6 | | 6.2 | 6.2.3 | | 7.0 | unaffected | |5 | unaffected |

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. 1. 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 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.

Acknowledgments

Paul Ryman of VMware Sydney Engineering Team

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-2019-1301

A security feature bypass vulnerability exists in Windows Defender Application Control (WDAC) which could allow an attacker to bypass WDAC enforcement, aka 'Windows Defender Application Control Security Feature Bypass Vulnerability'.

A security feature bypass vulnerability exists in Windows which could allow an attacker to bypass Device Guard, aka 'Windows Security Feature Bypass Vulnerability'. This CVE ID is unique from CVE-2019-0631, CVE-2019-0632.

A security feature bypass vulnerability exists in Windows which could allow an attacker to bypass Device Guard, aka 'Windows Security Feature Bypass Vulnerability'. This CVE ID is unique from CVE-2019-0627, CVE-2019-0632.

A security feature bypass vulnerability exists in Windows which could allow an attacker to bypass Device Guard, aka 'Windows Security Feature Bypass Vulnerability'. This CVE ID is unique from CVE-2019-0627, CVE-2019-0631.

A vulnerability exists in certain .Net Framework API's and Visual Studio in the way they parse URL's, aka '.NET Framework and Visual Studio Spoofing Vulnerability'.

A tampering vulnerability exists in PowerShell that could allow an attacker to execute unlogged code, aka "Microsoft PowerShell Tampering Vulnerability." This affects Windows 7, PowerShell Core 6.1, Windows Server 2012 R2, Windows RT 8.1, PowerShell Core 6.0, Windows Server 2019, Windows Server 2012, Windows 8.1, Windows Server 2016, Windows Server 2008 R2, Windows 10, Windows 10 Servers.

A remote code execution vulnerability exists when PowerShell improperly handles specially crafted files, aka "Microsoft PowerShell Remote Code Execution Vulnerability." This affects Windows RT 8.1, PowerShell Core 6.0, Microsoft.PowerShell.Archive 1.2.2.0, Windows Server 2016, Windows Server 2012, Windows Server 2008 R2, Windows Server 2019, Windows 7, Windows Server 2012 R2, PowerShell Core 6.1, Windows 10 Servers, Windows 10, Windows 8.1.

A flaw was found in .NET Core. An information disclosure vulnerability in a redirect when authentication information has been added manually to an Authorization header. An attacker who successfully exploited this vulnerability could use the information to further compromise the web application.

.NET Core 1.0, .NET Core 1.1, NET Core 2.0 and PowerShell Core 6.0.0 allow a denial of Service vulnerability due to how specially crafted requests are handled, aka ".NET Core Denial of Service Vulnerability".

.NET Core 1.0, 1.1 and 2.0 perform improper processing of XML documents. A remote unauthenticated attacker could exploit this vulnerability by issuing specially crafted requests to a .NET Core application.

References: https://nvd.nist.gov/vuln/detail/CVE-2018-0764 https://github.com/dotnet/core/blob/master/release-notes/2.0/2.0.5.md https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2018-0764 https://github.com/dotnet/corefx/commit/3f1155b

Microsoft .NET Framework 2.0 SP2, 3.0 SP2, 3.5, 3.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, .NET Core 1.0 and 2.0, and PowerShell Core 6.0.0 allow a security feature bypass vulnerability due to the way certificates are validated, aka ".NET Security Feature Bypass Vulnerability."