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

The X-AspNetMvc-Version header offers no operational value to end users and actively contributes to information leakage. Organizations deploying ASP.NET MVC should adopt header stripping as a standard hardening measure, aligning with principles of minimizing attack surface. The act of removal does not patch vulnerabilities but frustrates automated scanning and low-effort reconnaissance. The header is generated by the MvcHandler class,