CVE-2025-55184: Facebook React Server Components DoS Flaw

CVE-2025-55184 Overview

A pre-authentication denial of service vulnerability exists in React Server Components versions 19.0.0, 19.0.1, 19.1.0, 19.1.1, 19.1.2, 19.2.0, and 19.2.1. The vulnerability affects multiple React Server DOM packages including react-server-dom-parcel, react-server-dom-turbopack, and react-server-dom-webpack. The vulnerable code unsafely deserializes payloads from HTTP requests to Server Function endpoints, which can cause an infinite loop that hangs the server process and may prevent future HTTP requests from being served.

Critical Impact

Unauthenticated remote attackers can completely halt React server applications by sending specially crafted HTTP requests, causing service unavailability for all users.

Affected Products

• Facebook React 19.0.0, 19.0.1, 19.1.0, 19.1.1, 19.1.2, 19.2.0, 19.2.1
• Vercel Next.js 15.x (multiple versions including 15.6.0 canary releases)
• Vercel Next.js 16.x (including 16.1.0 and canary releases)

Discovery Timeline

• December 11, 2025 - CVE-2025-55184 published to NVD
• December 15, 2025 - Last updated in NVD database

Technical Details for CVE-2025-55184

Vulnerability Analysis

This vulnerability is classified as Insecure Deserialization (CWE-502) affecting React Server Components. The flaw exists in the deserialization logic that processes incoming HTTP request payloads targeting Server Function endpoints. When a maliciously crafted payload is submitted, the deserialization routine enters an infinite loop state, effectively freezing the Node.js event loop and preventing the server from processing any additional requests.

The impact is significant because the vulnerability requires no authentication to exploit—any remote attacker who can send HTTP requests to an affected server can trigger the condition. Once exploited, the server becomes completely unresponsive, requiring manual intervention to restore service. This makes it particularly dangerous for production applications where continuous availability is critical.

Root Cause

The root cause lies in the unsafe deserialization of untrusted data within the React Server DOM packages. When processing payloads sent to Server Function endpoints, the deserialization code fails to properly validate or limit the structure of incoming data. Certain payload structures can create self-referential or infinitely recursive patterns that the deserializer attempts to resolve indefinitely, causing the infinite loop condition.

Attack Vector

The attack vector is network-based and requires no user interaction or authentication. An attacker can exploit this vulnerability by sending a specially crafted HTTP POST request to any exposed Server Function endpoint. The attack is particularly effective because:

1. Server Functions are designed to receive arbitrary data from clients
2. The vulnerable deserialization occurs before any business logic validation
3. A single malicious request can freeze the entire server process
4. The attack can be executed from any network location with access to the target server

Due to the lack of verified exploit code, the specific payload structure that triggers the infinite loop is not detailed here. Refer to the React Security Blog Post for technical details on the vulnerability mechanics.

Detection Methods for CVE-2025-55184

Indicators of Compromise

• Sudden server unresponsiveness with active Node.js process consuming 100% CPU
• HTTP request timeouts affecting all endpoints simultaneously
• Event loop lag metrics showing extreme values or complete stall
• Unusual POST request patterns targeting Server Function endpoints before service interruption

Detection Strategies

• Monitor Node.js process CPU utilization and alert on sustained 100% usage patterns
• Implement event loop lag monitoring with alerts for lag exceeding normal thresholds
• Analyze HTTP access logs for unusual payload sizes or patterns in POST requests to Server Function routes
• Deploy application performance monitoring (APM) to detect deserialization anomalies

Monitoring Recommendations

• Configure health check endpoints external to the main event loop to detect server hangs
• Implement request timeout monitoring at the load balancer or reverse proxy level
• Set up automated alerting when server response times exceed defined SLAs
• Monitor memory and CPU metrics for the Node.js processes hosting React Server Components

How to Mitigate CVE-2025-55184

Immediate Actions Required

• Upgrade React to a patched version as specified in the vendor advisory
• Review and update all affected React Server DOM packages (react-server-dom-parcel, react-server-dom-turbopack, react-server-dom-webpack)
• If using Next.js, upgrade to a patched version that incorporates the React fix
• Deploy web application firewall (WAF) rules to filter potentially malicious payloads while awaiting patches

Patch Information

Patched versions are available from Facebook/Meta. Consult the Facebook Security Advisory and the React Blog Post for specific version numbers and upgrade instructions. Organizations should prioritize updating the following packages to their latest secure versions: react, react-dom, react-server-dom-parcel, react-server-dom-turbopack, and react-server-dom-webpack.

Workarounds

• Place affected applications behind a reverse proxy with aggressive request timeout settings to limit the duration of any single request
• Implement rate limiting on Server Function endpoints to reduce the attack surface
• Consider temporarily disabling Server Functions if they are not critical to application functionality
• Deploy the application with process managers that automatically restart unresponsive processes

# Example: Configure PM2 to restart unresponsive Node.js processes
# pm2.config.js
module.exports = {
  apps: [{
    name: "react-app",
    script: "server.js",
    max_memory_restart: "1G",
    listen_timeout: 10000,
    kill_timeout: 5000,
    wait_ready: true
  }]
}