REACT2SHELL (CVE-2025-55182): DETECTION & MITIGATION GUIDE

Summary from the TLDR InfoSec newsletter

React2Shell is a critical remote code execution flaw in React Server Components and related Next.js setups that allows an attacker to send a crafted HTTP request to a server-side function endpoint and execute arbitrary code on the backend. Systems are especially at risk when using React Server Functions with the use server directive or default Next.js App Router configurations, which expose vulnerable endpoints even in otherwise standard apps. The issue affects multiple React server DOM packages and a wide range of Next.js 15 and 16 versions. Fixed versions are already available. Upgrading these components is the primary mitigation.