Microsoft Security Advisory CVE-2025-55315: .NET Security Feature Bypass Vulnerability
Date: 2025-10
Affected: nuget/Microsoft.AspNetCore.Server.Kestrel.Core, nuget/Microsoft.AspNetCore.App.Runtime.win-x86, nuget/Microsoft.AspNetCore.App.Runtime.win-x64
Attack vector: other
Category: vulnerability-disclosure
Severity: Critical
CVE: CVE-2025-55315
CWE: CWE-444
CVSS: 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


Mitigations:

Architectural layers (MAESTRO):