Microsoft .NET Core and Visual Studio Denial-of-Service Vulnerability. Actively exploited: CISA added this vulnerability to its Known Exploited Vulnerabilities catalog on 09/08/2023. Patch affected systems as an emergency.
| Package | Affected versions | Patched versions |
|---|---|---|
| Microsoft.AspNetCore.App.Runtime.win-arm64 | ≥ 6.0.0, < 6.0.21≥ 7.0.0, < 7.0.10 | 6.0.217.0.10 |
| Microsoft.AspNetCore.App.Runtime.win-x64 | ≥ 6.0.0, < 6.0.21≥ 7.0.0, < 7.0.10 | 6.0.217.0.10 |
| Microsoft.AspNetCore.App.Runtime.win-x86 | ≥ 6.0.0, < 6.0.21≥ 7.0.0, < 7.0.10 | 6.0.217.0.10 |
| Microsoft.AspNetCore.Server.Kestrel.Transport.Libuv | ≥ 6.0.0, < 6.0.21< 2.1.40 | 6.0.212.1.40 |
| Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets | < 2.1.40 | 2.1.40 |
| .net | ≥ 6.0.0, < 6.0.21≥ 7.0.0, < 7.0.10 | 6.0.217.0.10 |
| asp.net core | ≥ 2.1, < 2.1.40 | 2.1.40 |
| visual studio 2022 | ≥ 17.2.0, < 17.2.18≥ 17.4.0, < 17.4.10≥ 17.6.0, < 17.6.6 | 17.2.1817.4.1017.6.6 |
Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core 2.1, .NET 6.0, and .NET 7.0. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.
A vulnerability exists in Kestrel where, on detecting a potentially malicious client, Kestrel will sometimes fail to disconnect it, resulting in denial of service.
Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/269
If your application is running behind a reverse proxy, or Web Application Firewall, which has its own mitigations against HTTP based attacks this issue may be mitigated by the proxy or WAF
If your application uses the following package versions, ensure you update to the latest version of .NET.
| Package name | Affected version | Patched version |
|---|---|---|
| Microsoft.AspNetCore.App.Runtime.win-arm64 | >= 7.0.0, <= 7.0.9 | 7.0.10 |
| Microsoft.AspNetCore.App.Runtime.win-x64 | >= 7.0.0, <= 7.0.9 | 7.0.10 |
| Microsoft.AspNetCore.App.Runtime.win-x86 | >= 7.0.0, <= 7.0.9 | 7.0.10 |
| Package name | Affected version | Patched version |
|---|---|---|
| Microsoft.AspNetCore.Server.Kestrel.Transport.Libuv |
Running one of these products? Scan your site to see whether it exposes a vulnerable version.
Scan my site free| >= 6.0.0, <= 6.0.20 |
| 6.0.21 |
| Microsoft.AspNetCore.App.Runtime.win-arm64 | >= 6.0.0, <= 6.0.20 | 6.0.21 |
| Microsoft.AspNetCore.App.Runtime.win-x64 | >= 6.0.0, <= 6.0.20 | 6.0.21 |
| Microsoft.AspNetCore.App.Runtime.win-x86 | >= 6.0.0, <= 6.0.20 | 6.0.21 |
| Package name | Affected version | Patched version |
|---|---|---|
| Microsoft.AspNetCore.Server.Kestrel.Transport.Libuv | <= 2.1.39 | 2.1.40 |
| Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets | <= 2.1.39 | 2.1.40 |
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.
dotnet --info command. You will see output like the following;.NET Core SDK (reflecting any global.json):
Version: 6.0.300
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\6.0.300\
Host (useful for support):
Version: 6.0.5
Commit: 8473146e7d
.NET Core SDKs installed:
6.0.300 [C:\Program Files\dotnet\sdk]
.NET Core runtimes installed:
Microsoft.AspNetCore.App 6.0.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 6.0.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
To install additional .NET Core runtimes or SDKs:
https://aka.ms/dotnet-download
.NET 6.0 and and .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.
If you have found a potential security issue in .NET 6.0 or .NET 7.0, please email details to [email protected]. 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.
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.
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.
V1.0 (August 08, 2023): Advisory published.
Version 1.0
Last Updated 2023-08-08