Automated vulnerability scanners frequently flag as a critical or high-severity security risk. This exact string—often captured from the X-AspNet-Version or X-Powered-By HTTP headers—triggers alarms for legacy bugs like remote code execution, cross-site scripting (XSS), and authentication bypasses.

If you cannot recompile an application, you must ensure the hosting the application has the latest Security and Quality Rollups installed. Microsoft continues to release rollups for .NET Framework versions 4.8 and 4.8.1 that address critical RCE vulnerabilities. As long as the latest patches are applied, the modern runtime remains secure despite the v4.0.30319 version header.

There is no security "hotfix" strategy for .NET 4.0. The only secure remediation is migration.

— .NET Framework Remote Code Execution

If an environment runs the product from 2010 rather than a newer 4.x runtime, it faces several high-severity security threats. Microsoft ended support for the standalone .NET Framework 4.0 package in 2016, leaving unpatched instances exposed to several classic attack vectors: 1. Remote Code Execution (RCE) via Deserialization