CVE-2025-55182

CVE-2025-55182 is a critical (CVSS 10.0) pre-authentication remote code execution flaw (CWE-502, deserialization of untrusted data) in React Server Components, specifically the react-server-dom-parcel, react-server-dom-turbopack, and react-server-dom-webpack packages in versions 19.0.0, 19.1.0, 19.1.1, and 19.2.0. It is triggered when the vulnerable code unsafely deserializes payloads from HTTP requests sent to Server Function endpoints, requiring no authentication or user interaction. An attacker gains arbitrary code execution on the affected server (CVSS scope changed, with high impact to confidentiality, integrity, and availability), and reporting notes a campaign in which hackers used the flaw to breach 766 Next.js hosts and steal credentials. Any React/Next.js application exposing Server Functions with the affected React versions is in scope, which given the ubiquity of React and Next.js is a very large deployed base. Exploitation is confirmed in the wild: the flaw was added to CISA's Known Exploited Vulnerabilities catalog on 2025-12-05 with known ransomware use, EPSS puts the 30-day exploitation probability at 99.8%, multiple public PoC/scanner repositories are available, and coverage has dubbed the flaw React2Shell.

What to do: Upgrade the react-server-dom-webpack, react-server-dom-parcel, and react-server-dom-turbopack packages to the vendor-patched releases (any version later than the vulnerable 19.0.0, 19.1.0, 19.1.1, and 19.2.0 line) and update Next.js per Vercel's advisory; as a KEV entry, U.S. federal agencies must apply vendor mitigations per BOD 22-01 or discontinue use. Audit internet-exposed Server Function endpoints for the vulnerable React versions and review logs for exploitation activity, including the reported campaign that breached 766 Next.js hosts and stole credentials, then rotate any exposed credentials.