Microsoft Security Advisory CVE-2020-1597 | ASP.NET Core Denial of Service Vulnerability
Executive summary
Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core. 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 ASP.NET Core improperly handles web requests. An attacker who successfully exploited this vulnerability could cause a denial of service against an ASP.NET Core web application. The vulnerability can be exploited remotely, without authentication.
A remote unauthenticated attacker could exploit this vulnerability by issuing specially crafted requests to the ASP.NET Core application.
The update addresses the vulnerability by correcting how the ASP.NET Core web application handles web requests.
Microsoft has not identified any mitigating factors for this vulnerability.
Affected software
Any .NET Core 3.1 application running on .NET Core 3.1.6 or lower
Any .NET Core 2.1 application running on .NET Core 2.1.20 or lower
Please note that .NET Core 3.0 is now out of support and all applications should be updated to 3.1.
How do I know if I am affected?
If you have a runtime or SDK with a version listed in affected software you are exposed to the vulnerability.
How do I fix the issue?
To fix the issue please install the latest version of .NET Core 3.1. If you have installed one or more .NET Core SDKs through Visual Studio, Visual Studio will prompt you to update Visual Studio which will also update your .NET Core SDKs.
You can list the versions you have installed by running the dotnet --info command. You will see output like the following;
.NET Core SDK (reflecting any global.json):
Version: 3.1.100
Commit: cd82f021f4
Runtime Environment:
OS Name: Windows
OS Version: 10.0.18363
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\3.1.100\
Host (useful for support):
Version: 3.1.0
Commit: 65f04fb6db
.NET Core SDKs installed:
3.1.100 [C:\Program Files\dotnet\sdk]
.NET Core runtimes installed:
Microsoft.AspNetCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
To install additional .NET Core runtimes or SDKs:
https://aka.ms/dotnet-download
Once you have installed the updated runtime or SDK, restart your apps for the update to take effect.
Additionally, if you've deployed self-contained applications targeting any of the impacted versions, these applications are also vulnerable and must be recompiled and redeployed.
Other Information
Reporting Security Issues
If you have found a potential security issue in .NET Core, please email details to secure@microsoft.com. Reports may qualify for the .NET Core Bug Bounty. Details of the .NET Core Bug Bounty including terms and conditions are at https://aka.ms/corebounty.
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.
Microsoft Security Advisory CVE-2020-1597 | ASP.NET Core Denial of Service Vulnerability
Executive summary
Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core. 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 ASP.NET Core improperly handles web requests. An attacker who successfully exploited this vulnerability could cause a denial of service against an ASP.NET Core web application. The vulnerability can be exploited remotely, without authentication.
A remote unauthenticated attacker could exploit this vulnerability by issuing specially crafted requests to the ASP.NET Core application.
The update addresses the vulnerability by correcting how the ASP.NET Core web application handles web requests.
Discussion
Discussion for this issue can be found at https://github.com/dotnet/aspnetcore/issues/24796
Mitigation factors
Microsoft has not identified any mitigating factors for this vulnerability.
Affected software
Please note that .NET Core 3.0 is now out of support and all applications should be updated to 3.1.
How do I know if I am affected?
If you have a runtime or SDK with a version listed in affected software you are exposed to the vulnerability.
How do I fix the issue?
To fix the issue please install the latest version of .NET Core 3.1. If you have installed one or more .NET Core SDKs through Visual Studio, Visual Studio will prompt you to update Visual Studio which will also update your .NET Core SDKs.
You can list the versions you have installed by running the
dotnet --infocommand. You will see output like the following;Once you have installed the updated runtime or SDK, restart your apps for the update to take effect.
Additionally, if you've deployed self-contained applications targeting any of the impacted versions, these applications are also vulnerable and must be recompiled and redeployed.
Other Information
Reporting Security Issues
If you have found a potential security issue in .NET Core, please email details to secure@microsoft.com. Reports may qualify for the .NET Core Bug Bounty. Details of the .NET Core Bug Bounty including terms and conditions are at https://aka.ms/corebounty.
Support
You can ask questions about this issue on GitHub in the .NET Core GitHub organization. The main repos are located at https://github.com/dotnet/runtime and https://github.com/dotnet/aspnet/. The Announcements repo (https://github.com/dotnet/Announcements) will contain this bulletin as an issue and will include a link to a discussion issue. You can ask questions in the linked discussion issue.
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.
External Links
CVE-2020-1597
Revisions
V1.0 (August 11, 2020): Advisory published.
Version 1.0
Last Updated 2020-08-11