Description

Microsoft Security Advisory CVE-2025-55315: .NET Security Feature Bypass Vulnerability # Microsoft Security Advisory CVE-2025-55315: .NET Security Feature Bypass Vulnerability ## Executive summary Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core 10.0 , ASP.NET Core 9.0 , ASP.NET Core 8.0, and ASP.NET Core 2.3. This advisory also provides guidance on what developers can do to update their applications to address this vulnerability. Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an authorized attacker to bypass a security feature over a network. ## Discussion Discussion for this issue can be found at https://github.com/dotnet/announcements/issues/371 ### Mitigation factors Microsoft has not identified any mitigating factors for this vulnerability. ## Affected software * Any ASP.NET Core 10.0 application running on ASP.NET Core 10.0.0-rc.1.25451.107 or earlier. * Any ASP.NET Core 9.0 application running on ASP.NET Core 9.0.9 or earlier. * Any ASP.NET Core application running on ASP.NET Core 8.0.20 or earlier. * Any ASP.NET Core 2.x application consuming the package Microsoft.AspNetCore.Server.Kestrel.Core version 2.3.0 or earlier. ## Affected Packages The vulnerability affects any Microsoft .NET Core project if it uses any of affected packages versions listed below Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.AspNetCore.Server.Kestrel.Core | <= 2.3.0 | 2.3.6 ### ASP.NET Core 10 Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.AspNetCore.App.Runtime.linux-arm | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107 Microsoft.AspNetCore.App.Runtime.linux-arm64 | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107 Microsoft.AspNetCore.App.Runtime.linux-musl-arm | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107 Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107 Microsoft.AspNetCore.App.Runtime.linux-musl-x64 | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107 Microsoft.AspNetCore.App.Runtime.linux-x64 | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107 Microsoft.AspNetCore.App.Runtime.osx-arm64 | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107 Microsoft.AspNetCore.App.Runtime.osx-x64 | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107 Microsoft.AspNetCore.App.Runtime.win-arm | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107 Microsoft.AspNetCore.App.Runtime.win-arm64 | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107 Microsoft.AspNetCore.App.Runtime.win-x64 | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107 Microsoft.AspNetCore.App.Runtime.win-x86 | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107 ### ASP.NET Core 9 Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.AspNetCore.App.Runtime.linux-arm | >= 9.0.0, <= 9.0.9 | 9.0.10 Microsoft.AspNetCore.App.Runtime.linux-arm64 | >= 9.0.0, <= 9.0.9 | 9.0.10 Microsoft.AspNetCore.App.Runtime.linux-musl-arm | >= 9.0.0, <= 9.0.9 | 9.0.10 Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 | >= 9.0.0, <= 9.0.9 | 9.0.10 Microsoft.AspNetCore.App.Runtime.linux-musl-x64 | >= 9.0.0, <= 9.0.9 | 9.0.10 Microsoft.AspNetCore.App.Runtime.linux-x64 | >= 9.0.0, <= 9.0.9 | 9.0.10 Microsoft.AspNetCore.App.Runtime.osx-arm64 | >= 9.0.0, <= 9.0.9 | 9.0.10 Microsoft.AspNetCore.App.Runtime.osx-x64 | >= 9.0.0, <= 9.0.9 | 9.0.10 Microsoft.AspNetCore.App.Runtime.win-arm | >= 9.0.0, <= 9.0.9 | 9.0.10 Microsoft.AspNetCore.App.Runtime.win-arm64 | >= 9.0.0, <= 9.0.9 | 9.0.10 Microsoft.AspNetCore.App.Runtime.win-x64 | >= 9.0.0, <= 9.0.9 | 9.0.10 Microsoft.AspNetCore.App.Runtime.win-x86 | >= 9.0.0, <= 9.0.9 | 9.0.10 ### ASP.NET Core 8 Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.AspNetCore.App.Runtime.linux-arm | >= 8.0.0, <= 8.0.20 | 8.0.21 Microsoft.AspNetCore.App.Runtime.linux-arm64 | >= 8.0.0, <= 8.0.20 | 8.0.21 Microsoft.AspNetCore.App.Runtime.linux-musl-arm | >= 8.0.0, <= 8.0.20 | 8.0.21 Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 | >= 8.0.0, <= 8.0.20 | 8.0.21 Microsoft.AspNetCore.App.Runtime.linux-musl-x64 | >= 8.0.0, <= 8.0.20 | 8.0.21 Microsoft.AspNetCore.App.Runtime.linux-x64 | >= 8.0.0, <= 8.0.20 | 8.0.21 Microsoft.AspNetCore.App.Runtime.osx-arm64 | >= 8.0.0, <= 8.0.20 | 8.0.21 Microsoft.AspNetCore.App.Runtime.osx-x64 | >= 8.0.0, <= 8.0.20 | 8.0.21 Microsoft.AspNetCore.App.Runtime.win-arm | >= 8.0.0, <= 8.0.20 | 8.0.21 Microsoft.AspNetCore.App.Runtime.win-arm64 | >= 8.0.0, <= 8.0.20 | 8.0.21 Microsoft.AspNetCore.App.Runtime.win-x64 | >= 8.0.0, <= 8.0.20 | 8.0.21 Microsoft.AspNetCore.App.Runtime.win-x86 | >= 8.0.0, <= 8.0.20 | 8.0.21 ## Advisory FAQ ### 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 or affected packages, you're exposed to the vulnerability. ### How do I fix the issue? 1. To fix the issue please install the latest version of .NET 9.0 and .NET 8.0. 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. 2. If your application references the vulnerable package, update the package reference to the patched version. * You can list the versions you have installed by running the dotnet --info command. You will see output like the following; .NET SDK: Version: 9.0.100 Commit: 59db016f11 Workload version: 9.0.100-manifests.3068a692 MSBuild version: 17.12.7+5b8665660 Runtime Environment: OS Name: Mac OS X OS Version: 15.2 OS Platform: Darwin RID: osx-arm64 Base Path: /usr/local/share/dotnet/sdk/9.0.100/ .NET workloads installed: There are no installed workloads to display. Configured to use loose manifests when installing new manifests. Host: Version: 9.0.0 Architecture: arm64 Commit: 9d5a6a9aa4 .NET SDKs installed: 9.0.100 [/usr/local/share/dotnet/sdk] .NET runtimes installed: Microsoft.AspNetCore.App 9.0.0 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App] Microsoft.NETCore.App 9.0.0 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App] Other architectures found: x64 [/usr/local/share/dotnet] registered at [/etc/dotnet/install_location_x64] Environment variables: Not set global.json file: Not found Learn more: https://aka.ms/dotnet/info Download .NET: https://aka.ms/dotnet/download * If you're using .NET 8.0, you should download and install .NET 8.0.21 Runtime or .NET 8.0.318 SDK (for Visual Studio 2022 v17.10 latest update) from https://dotnet.microsoft.com/download/dotnet-core/8.0. * If you're using .NET 9.0, you should download and install .NET 9.0.10 Runtime or .NET 9.0.111 SDK (for Visual Studio 2022 v17.12 latest update) from https://dotnet.microsoft.com/download/dotnet-core/9.0. * If you're using .NET 10.0, you should download and install .NET 10.0.0-rc.2.25476.107 Runtime or .NET 10.0.100-rc.2.25476.107 SDK (for Visual Studio 2022 v17.12 latest update) from https://dotnet.microsoft.com/download/dotnet-core/10.0. * If you're using Microsoft.AspNetCore.Server.Kestrel.Core nuget package, update to the latest version 2.3.6 using either of the following methods: * Using the NuGet Package Manager UI in Visual Studio: - Open your project in Visual Studio. - Right-click on your project in Solution Explorer and select "Manage NuGet Packages..." or navigate to "Project > Manage NuGet Packages". - In the NuGet Package Manager window, select the "Updates" tab. This tab lists packages with available updates from your configured package sources. - Select the package(s) you wish to update. You can choose a specific version from the dropdown or update to the latest available version. - Click the "Update" button. * Using the NuGet Package Manager Console in Visual Studio: - Open your project in Visual Studio. - Navigate to "Tools > NuGet Package Manager > Package Manager Console". - To update a specific package to its latest version, use the Update-Package command: Code: Update-Package -Id Microsoft.AspNetCore.Server.Kestrel.Core * Using the .NET CLI (Command Line Interface): Open a terminal or command

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