GitHub Security Advisory: GHSA-5rrx-jjjq-q2r5
Package: Microsoft.AspNetCore.Server.Kestrel.Core (NUGET)
Severity: CRITICAL (CVSS 9.9)
CWE: CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Vulnerable versions: <= 2.3.0
Patched in: 2.3.6

Summary: Microsoft Security Advisory CVE-2025-55315: .NET Security Feature Bypass Vulnerability

Details:
# 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