Both React and Blazor applications can be secure, but neither is secure by default. Their security depends far more on how they are designed, configured, and maintained than on the framework itself.
In Blazor Server, for instance, applications run in server memory, with multiple user sessions hosted within the same server process. Each interaction is processed in its own “circuit,” which is responsible for isolating sessions using its own dependency injection scope.
While this makes it possible for Blazor Server apps to provide deep and dynamic user experiences, this approach is not without its challenges in terms of app architecture. Microsoft itself does not advise co-hosting apps on the same server and sharing state using singleton services without strict safeguards in place. The major reason is that this could result in serious security issues, such as the exposure of one user’s information to another.
Another important consideration is resource management. If not properly managed, Blazor applications can be vulnerable to CPU exhaustion. To mitigate this issue, developers usually rely on built-in request timeouts and connection limits. Such protections are not in place by default in Blazor Server applications. This means developers must establish these parameters before engaging in CPU-intensive activities.
React applications also encounter a variety of security issues. A serious unauthorised remote code execution vulnerability was found in React Server Components in December 2025. Such a problem arose due to the decoding of payloads in React Server Function endpoints and took almost a week to fix. This situation indicates the potential posed by constantly evolving ecosystems as well as the React community’s readiness in addressing such issues.
Vercel, the company behind Next.js, is not as mature as Microsoft in terms of enterprise governance and security processes. As a result, responses to critical incidents may take longer—as was the case in the previous incident, where the response took more than a week. For organizations operating in regulated or security-sensitive environments, such delays can introduce additional risk and should be carefully considered when choosing a technology stack.
That said, neither React nor Blazor is “automatically secure”. Blazor demands strong server-side design and resource management, and React is very much dependent on keeping up with changes in a very dynamic environment. In both situations, security is less about the framework itself and more about how carefully your developers address it.
Leobit
