X-aspnetmvc-version May 2026

Abstract: The X-AspNetMvc-Version HTTP header is a custom response header automatically injected by ASP.NET MVC frameworks. While intended to aid debugging and runtime environment identification, this header constitutes a form of information disclosure that can aid malicious actors in reconnaissance. This paper examines the header’s origin, technical function, associated security risks, and industry-standard mitigation techniques.

The header is generated by the MvcHandler class, responsible for processing MVC requests. When the Application_Start method initializes the routing table, the framework binds the version string (e.g., 5.2 , 4.0 , 3.0 ) from the assembly's AssemblyFileVersionAttribute . This value is appended to the outgoing response collection. Unlike the X-AspNet-Version header (which reports .NET runtime version), X-AspNetMvc-Version is specific to the MVC library. x-aspnetmvc-version

curl -I https://example.com | grep -i X-AspNetMvc Expected output: (none). Abstract: The X-AspNetMvc-Version HTTP header is a custom

In the client-server web model, HTTP headers convey metadata about requests and responses. Most production web applications strive to minimize revealing internal infrastructure details. However, default configurations of ASP.NET MVC (versions 3 through 5) implicitly add the X-AspNetMvc-Version header to every HTTP response. This value corresponds directly to the version of the System.Web.Mvc assembly used. The header is generated by the MvcHandler class,

protected void Application_EndRequest()