ASP.NET Security Feature Bypass Vulnerability

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

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.

Source published

14 Oct 2025 17:00:10 UTC

Source modified

22 Feb 2026 17:24:12 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 9.9 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L/E:U/RL:O/RC:C

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.

Source published

Oct 14, 2025, 5:00:10 PM (timezone not stated)

Source modified

Feb 22, 2026, 5:24:12 PM (timezone not stated)

Observed here

9 Nov 2026 03:11:38 UTC

Source terms

ENISA EUVD · source terms and attribution apply

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 9.9 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L/E:U/RL:O/RC:C

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.

Source published

14 Oct 2025 17:15:44 UTC

Source modified

18 Oct 2026 21:10:00 UTC

Observed here

25 Oct 2026 03:17:11 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 9.9 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L

# Microsoft Security Advisory CVE-2025-55315: .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 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 ### <a name="mitigation-factors"></a>Mitigation factors Microsoft has not identified any mitigating factors for this vulnerability. ## <a name="affected-software"></a>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. ## <a name="affected-packages"></a>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](https://www.nuget.org/packages/Microsoft.AspNetCore.Server.Kestrel.Core) | <= 2.3.0 | 2.3.6 ### <a name="ASP.NET Core 10"></a>ASP.NET Core 10 Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- [Microsoft.AspNetCore.App.Runtime.linux-arm](https://www.nuget.org/packages/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](https://www.nuget.org/packages/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](https://www.nuget.org/packages/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](https://www.nuget.org/packages/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](https://www.nuget.org/packages/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](https://www.nuget.org/packages/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](https://www.nuget.org/packages/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](https://www.nuget.org/packages/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](https://www.nuget.org/packages/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](https://www.nuget.org/packages/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](https://www.nuget.org/packages/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](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x86) | 10.0.0-rc.1.25451.107 | 10.0.0-rc.2.25502.107 ### <a name="ASP.NET Core 9"></a>ASP.NET Core 9 Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- [Microsoft.AspNetCore.App.Runtime.linux-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm) | >= 9.0.0, <= 9.0.9 | 9.0.10 [Microsoft.AspNetCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm64) | >= 9.0.0, <= 9.0.9 | 9.0.10 [Microsoft.AspNetCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm) | >= 9.0.0, <= 9.0.9 | 9.0.10 [Microsoft.AspNetCore.App.Runtime.linux-musl-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm64) | >= 9.0.0, <= 9.0.9 | 9.0.10 [Microsoft.AspNetCore.App.Runtime.linux-musl-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-x64) | >= 9.0.0, <= 9.0.9 | 9.0.10 [Microsoft.AspNetCore.App.Runtime.linux-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-x64) | >= 9.0.0, <= 9.0.9 | 9.0.10 [Microsoft.AspNetCore.App.Runtime.osx-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-arm64) | >= 9.0.0, <= 9.0.9 | 9.0.10 [Microsoft.AspNetCore.App.Runtime.osx-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-x64) | >= 9.0.0, <= 9.0.9 | 9.0.10 [Microsoft.AspNetCore.App.Runtime.win-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm) | >= 9.0.0, <= 9.0.9 | 9.0.10 [Microsoft.AspNetCore.App.Runtime.win-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm64) | >= 9.0.0, <= 9.0.9 | 9.0.10 [Microsoft.AspNetCore.App.Runtime.win-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x64) | >= 9.0.0, <= 9.0.9 | 9.0.10 [Microsoft.AspNetCore.App.Runtime.win-x86](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x86) | >= 9.0.0, <= 9.0.9 | 9.0.10 ### <a name="ASP.NET Core 8"></a>ASP.NET Core 8 Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- [Microsoft.AspNetCore.App.Runtime.linux-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm) | >= 8.0.0, <= 8.0.20 | 8.0.21 [Microsoft.AspNetCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm64) | >= 8.0.0, <= 8.0.20 | 8.0.21 [Microsoft.AspNetCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm) | >= 8.0.0, <= 8.0.20 | 8.0.21 [Microsoft.AspNetCore.App.Runtime.linux-musl-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm64) | >= 8.0.0, <= 8.0.20 | 8.0.21 [Microsoft.AspNetCore.App.Runtime.linux-musl-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-x64) | >= 8.0.0, <= 8.0.20 | 8.0.21 [Microsoft.AspNetCore.App.Runtime.linux-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-x64) | >= 8.0.0, <= 8.0.20 | 8.0.21 [Microsoft.AspNetCore.App.Runtime.osx-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-arm64) | >= 8.0.0, <= 8.0.20 | 8.0.21 [Microsoft.AspNetCore.App.Runtime.osx-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-x64) | >= 8.0.0, <= 8.0.20 | 8.0.21 [Microsoft.AspNetCore.App.Runtime.win-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm) | >= 8.0.0, <= 8.0.20 | 8.0.21 [Microsoft.AspNetCore.App.Runtime.win-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm64) | >= 8.0.0, <= 8.0.20 | 8.0.21 [Microsoft.AspNetCore.App.Runtime.win-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x64) | >= 8.0.0, <= 8.0.20 | 8.0.21 [Microsoft.AspNetCore.App.Runtime.win-x86](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x86) | >= 8.0.0, <= 8.0.20 | 8.0.21 ## 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](#affected-packages) or [affected packages](#affected-software), you're exposed to the vulnerability. ### <a name="how-fix"></a>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](https://www.nuget.org/packages/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 prompt in your project's directory. To update a specific package to its latest version: Code: dotnet add package Microsoft.AspNetCore.Server.Kestrel.Core 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](https://docs.microsoft.com/dotnet/core/deploying/#self-contained-deployments-scd) 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, .NET 9.0 or .NET 10.0, 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>. ### 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/aspnetcore. 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 ### Acknowledgement Sid [CVE-2025-55315]( https://www.cve.org/CVERecord?id=CVE-2025-55315) ### Revisions V1.0 (October 14, 2025): Advisory published. _Version 1.0_ _Last Updated 2025-10-14_

Source published

14 Oct 2025 20:32:06 UTC

Source modified

10 Sep 2026 03:50:38 UTC

Observed here

23 Oct 2026 16:01:25 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L

Publisher rating · CRITICAL