. While seeing this header often triggers "outdated version" warnings in security scanners, it is frequently a false positive if the underlying .NET Framework has been patched. Critical Vulnerabilities Associated with CLR 4.0.30319
The X-AspNet-Version: 4.0.30319 header is , but it is a powerful reconnaissance tool that lowers the barrier to exploiting real vulnerabilities like view state deserialization and padding oracle attacks. Removing the header is a low-effort, high-value security hardening measure. Organizations still exposing this header on production ASP.NET applications should prioritize its removal and conduct a full security review of their .NET runtime configuration.
According to Wappalyzer and BuiltWith data, over 18% of detected ASP.NET sites still emit the X-AspNet-Version header, with a significant portion running actual 4.0.x runtime libraries.
A critical nuance: The version number 4.0.30319 is . It does not change even if you upgrade to .NET 4.5, 4.6, 4.7, or 4.8 on the same server . Microsoft maintained the same version string for compatibility reasons. Therefore, a server emitting 4.0.30319 could be running:
Kysy tuotteesta
X-aspnet-version 4.0.3 Vulnerabilities [2021] Info
. While seeing this header often triggers "outdated version" warnings in security scanners, it is frequently a false positive if the underlying .NET Framework has been patched. Critical Vulnerabilities Associated with CLR 4.0.30319
The X-AspNet-Version: 4.0.30319 header is , but it is a powerful reconnaissance tool that lowers the barrier to exploiting real vulnerabilities like view state deserialization and padding oracle attacks. Removing the header is a low-effort, high-value security hardening measure. Organizations still exposing this header on production ASP.NET applications should prioritize its removal and conduct a full security review of their .NET runtime configuration. x-aspnet-version 4.0.3 vulnerabilities
According to Wappalyzer and BuiltWith data, over 18% of detected ASP.NET sites still emit the X-AspNet-Version header, with a significant portion running actual 4.0.x runtime libraries. Removing the header is a low-effort, high-value security
A critical nuance: The version number 4.0.30319 is . It does not change even if you upgrade to .NET 4.5, 4.6, 4.7, or 4.8 on the same server . Microsoft maintained the same version string for compatibility reasons. Therefore, a server emitting 4.0.30319 could be running: A critical nuance: The version number 4
