Inside CVE-2025-55182: Weaponising the React2Shell RCE

React2Shell (CVE-2025-55182) started as an interesting edge case in server-side rendering and ended as a full remote code execution primitive. In this write-up I walk through the discovery process, the root cause in the rendering pipeline, and how I chained an initial input validation gap into arbitrary code execution on the server. I also cover the tooling I built afterward: a lightweight scanner that safely fingerprints affected targets without triggering the payload, intended purely for defenders to assess exposure. Responsible disclosure timeline, patch analysis, and detection guidance for blue teams are included at the end of this post.