.NET is Microsoft’s software-development platform: a runtime, standard libraries, language support, and application frameworks used to build web services, APIs, desktop software, and other applications. The name covers modern, cross-platform .NET as well as the older Windows-focused .NET Framework, which have different release and support paths and should be distinguished during vulnerability management.
Security exposure can arise in the runtime, ASP.NET request-handling components, application configuration, and third-party NuGet packages. Vulnerabilities may enable code execution, denial of service, or unauthorized access when affected components are reachable or incorrectly used; insecure deserialization and weak authentication or authorization are recurring application-level concerns. Operators should inventory the exact runtime and framework versions, apply supported security updates, monitor transitive dependencies, and remove obsolete components. Developers should use platform-provided cryptography and TLS appropriately, validate untrusted input, protect secrets outside source code, and configure authentication and authorization explicitly.