Microsoft warns Windows administrators about the increasing risks posed by organizations that continue to use outdated .NET versions.
In a recent post on the official IIS Support Blog, the company writes that many environments still appear to be dependent on runtimes that have reached the end of their useful life. This is particularly evident during security scans and compliance checks. Old .NET installations are increasingly becoming a vulnerability.
According to Microsoft, the problem is exacerbated by the way modern .NET versions are deployed. Unlike the earlier .NET Framework, modern .NET is no longer part of Windows itself. Applications only install the versions they need. This allows different releases to coexist. While this certainly provides flexibility, it also means that outdated components continue to run unnoticed, even when newer versions are available.
Recommendation: explicitly update software
Installing the latest runtime is not enough to make applications switch over. Microsoft emphasizes that software must be explicitly updated and re-released before it can use a newer .NET version. This remains the responsibility of development teams, not system administrators.
The blog advises administrators to actively check which applications are still running on an outdated runtime and to pass on those findings to the relevant developers or suppliers. Once applications have been updated and returned to production, it must be confirmed that no processes remain dependent on old versions. Only then can the relevant runtimes be safely removed from the environment.
Microsoft states that using unsupported .NET versions poses significant risks. Security issues are unresolved, technical support has been discontinued, and organizations may encounter problems during audits. The company, therefore, calls on organizations to structurally organize their .NET installations so that old components do not become a weak spot in their infrastructure.