ASP.NET Core Denial of Service Vulnerability

Microsoft Security Advisory CVE-2023-36558: .NET Security Feature Bypass Vulnerability

<a name="executive-summary"></a>Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core 6.0, ASP.NET Core 7.0 and, ASP.NET Core 8.0 RC2. This advisory also provides guidance on what developers can do to update their applications to address this vulnerability.

A security feature bypass vulnerability exists in ASP.NET where an unauthenticated user is able to bypass validation on Blazor server forms which could trigger unintended actions.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/288

<a name="mitigation-factors"></a>Mitigation factors

This vulnerability only affects ASP.NET Core Blazor apps. Other application types, including ASP.NET Core apps which do not utilize Blazor, are not affected.

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

Any ASP.NET Core Blazor 6.0 application running on .NET 6.0.24 or earlier. Any ASP.NET Core Blazor 7.0 application running on .NET 7.0.13 or earlier. Any ASP.NET Core Blazor 8.0 application running on .NET 8.0 RC2.

If your application uses the following package versions, ensure you update to the latest version of .NET.

<a name=".NET 7"></a>.NET 8.0

Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.AspNetCore.Components | 8.0.0-rc.2.23480.2 | 8.0.0

<a name=".NET 7"></a>.NET 7.0

Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.AspNetCore.Components | >= 7.0.0, < 7.0.13> | 7.0.14

<a name=".NET 7"></a>.NET 6.0

Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.AspNetCore.Components | >= 6.0.0, < 6.0.24 | 6.0.25

Advisory FAQ

<a name="how-affected"></a>How do I know if I am affected?

If you have a runtime or SDK with a version listed, or an affected package listed in affected software, you're exposed to the vulnerability.

<a name="how-fix"></a>How do I fix the issue?

To fix the issue please install the latest version of .NET 6.0 or .NET 7.0. If you have installed one or more .NET SDKs through Visual Studio, Visual Studio will prompt you to update Visual Studio, which will also update your .NET SDKs. If you are using one of the affected packages, please update to the patched version listed above. If you have .NET 6.0 or greater installed, 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: 7.0.200 Commit: 8473146e7d

Runtime Environment:

OS Name: Windows OS Version: 10.0.18363 OS Platform: Windows RID: win10-x64 Base Path: C:\Program Files\dotnet\sdk\7.0.300\

Host (useful for support):

Version: 76.0.5 Commit: 8473146e7d

.NET Core SDKs installed:

7.0.200 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:

Microsoft.AspNetCore.App 7.0.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.NETCore.App 7.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.WindowsDesktop.App 7.0.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET Core runtimes or SDKs: https://aka.ms/dotnet-download

If you're using .NET 8.0, you should download and install .NET 8.0.0 Runtime or .NET 8.0.100 SDK (for Visual Studio 2022 v17.8) from https://dotnet.microsoft.com/download/dotnet-core/8.0. If you're using .NET 7.0, you should download and install Runtime 7.0.14 or SDK 7.0.114 (for Visual Studio 2022 v17.4) from https://dotnet.microsoft.com/download/dotnet-core/7.0. If you're using .NET 6.0, you should download and install Runtime 6.0.25 or SDK 6.0.317 (for Visual Studio 2022 v17.2) from https://dotnet.microsoft.com/download/dotnet-core/6.0.

.NET 7.0 updates are also available from Microsoft Update. To access this either type "Check for updates" in your Windows search, or open Settings, choose Update & Security and then click Check for Updates.

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 8.0 or .NET 7.0 or .NET 6.0, please email details to secure@microsoft.com. Reports may qualify for the Microsoft .NET Core & .NET 5 Bounty. Details of the Microsoft .NET Bounty Program including terms and conditions are at <https://aka.ms/corebounty>.

Support

You can ask questions about this issue on GitHub in the .NET 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-2023-36558

Revisions

V1.0 (November 14, 2023): Advisory published.

Version 1.0

Last Updated 2023-11-14

ASP.NET Core and Visual Studio Elevation of Privilege Vulnerability

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A denial of service vulnerability exists when ASP.NET Core improperly handles web requests, aka 'ASP.NET Core Denial of Service Vulnerability'.

An elevation of privilege vulnerability exists when a ASP.NET Core web application, created using vulnerable project templates, fails to properly sanitize web requests, aka 'ASP.NET Core Elevation Of Privilege Vulnerability'.

A spoofing vulnerability exists in ASP.NET Core that could lead to an open redirect, aka 'ASP.NET Core Spoofing Vulnerability'.

A denial of service vulnerability exists when ASP.NET Core improperly handles web requests, aka 'ASP.NET Core Denial of Service Vulnerability'.

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