UNDERSTANDING THE RCE FLAW IN REACT SERVER FUNCTIONS

Summary from the TLDR Dev newsletter

CVE‑2025‑55182 is a critical Remote Code Execution vulnerability in React 19 Server Component infrastructure prior to the December 2025 security patch. The vulnerability is unauthenticated and pre-render. A single crafted HTTP request to a Server Function endpoint is enough, making it a high-severity vulnerability for production applications. This post explains how the vulnerability works in detail, details how it was fixed, and lists mitigation steps.