The header explicitly reveals the ASP.NET runtime version to any client, including malicious actors.
While this header was originally intended for debugging and compatibility purposes, in the hands of a malicious actor, it serves as a reconnaissance tool. It tells the attacker exactly which weapon to select from their arsenal.
This header is benign in isolation but becomes a critical weakness when combined with other misconfigurations or outdated patches.
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The primary risk of the header itself is . By revealing your technology stack, you provide "breadcrumbs" for attackers: Shhh… don't let your response headers talk too loudly
X-AspNet-Version: 4.0.30319 HTTP response header indicates that an application is running on the .NET Common Language Runtime (CLR) 4.0
Security Research Division Date: March 2025 Classification: Technical White Paper