# this is the worst case scenario

Source: https://www.youtube.com/watch?v=s81dVUM-cQM
Recap page: https://rapidrecap.app/video/s81dVUM-cQM
Generated: 2025-12-08T21:34:26.193+00:00

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## Quick Overview

The critical React2Shell vulnerability (CVE-2025-55182) allows for Remote Code Execution (RCE) in Next.js applications using React Server Components by exploiting insecure prototype references during deserialization of the React Flight Protocol, enabling an attacker to execute arbitrary code on the server by sending a specially crafted payload.

**Key Points:**
- The vulnerability, React2Shell (CVE-2025-55182), is a critical RCE flaw affecting React Server Components (RSC) in React and Next.js.
- The exploit targets the deserialization of the React Flight Protocol, allowing an attacker to send a payload that results in executing arbitrary JavaScript code on the server.
- The core issue stems from React failing to verify if requested keys exist on the object during chunk traversal while resolving references, allowing access to the object's prototype.
- The proof-of-concept payload leverages features like `__proto__:constructor` to retrieve the Function constructor and then uses fields like `_prefix` and `_formData.get` to construct a gadget that executes `child_process.execSync('calc')`.
- The vulnerability is particularly severe because the malicious deserialization occurs before the requested action is validated in `getActionOrError`, making simple header checks insufficient.
- Affected Next.js versions using the App Router include 15.x, 16.x, and Next.js 14.3.0-canary-77 and later canary releases; users must upgrade to patched versions like Next.js 15.0.5 or 19.0.1 for react-server-dom.
- The presenter praises Moritz Sanft (msanft) for publishing a very good write-up and Proof of Concept (PoC) for the vulnerability.

![Screenshot at 00:02: The video displays the Wiz blog post titled "React2Shell \(CVE-2025-55182\): Everything You Need to Know About the Critical React Vulnerability," setting the context for the technical discussion on the remote code execution flaw.](https://ss.rapidrecap.app/screens/s81dVUM-cQM/00-00-02.png)

**Context:** The video explains the critical React2Shell vulnerability (CVE-2025-55182) discovered in React Server Components (RSC) and its impact on Next.js applications using the App Router. The presenter details the mechanism of the exploit, which involves manipulating the serialization/deserialization process of the React Flight Protocol to achieve arbitrary code execution on the server by leveraging prototype pollution.

## Detailed Analysis

The video analyzes the critical React2Shell vulnerability (CVE-2025-55182), which affects React Server Components (RSC) as implemented in frameworks like Next.js. The vulnerability arises because the React Flight Protocol's deserialization process fails to adequately validate untrusted inputs when traversing chunks and resolving references. Specifically, React did not verify if a requested key was actually set on the object, allowing an attacker to access the object's prototype. This prototype pollution vulnerability allows an attacker to leverage the function constructor to execute arbitrary code (RCE) on the server. The presenter demonstrates the exploit chain using a crafted payload that references `__proto__:constructor` to gain access to the `Function` constructor. The payload utilizes properties like `_prefix` and `_formData.get` to chain calls, ultimately executing `f.process.mainModule.require('child_process').execSync('calc')`. The presenter notes that this is particularly dangerous because the unsafe deserialization happens before the requested action is validated. Affected versions of Next.js using the App Router are detailed, ranging from 15.x and 16.x to specific canary releases, with recommended patches provided by the Next.js team. The video also briefly shows the sponsor, Flare, a threat exposure management platform.

### Vulnerability Context

- React2Shell (CVE-2025-55182)
- Critical RCE in React Server Components (RSC) affecting Next.js App Router
- Exploits insecure prototype references during deserialization of the React Flight Protocol

### Exploit Mechanism

- Attacker sends crafted serialized chunks referencing `__proto__:constructor`
- Leverages deserialization to gain access to the Function constructor
- Uses properties like `_prefix` and `_formData.get` to chain methods and execute arbitrary code via `child_process.execSync('calc')`

### Vulnerability Root Cause

- React failed to verify if requested keys were actually set on the object during reference resolution in chunk traversal
- This allowed retrieving object prototypes.

### Affected Versions (Next.js App Router)

- Next.js 15.x, 16.x, and 14.3.0-canary-77 and later canary releases
- Patched versions include 15.0.5, 16.0.7, 19.0.1, 19.1.2, and 19.2.1 for react-server-dom.

### Mitigation

- Users must upgrade to the latest patched version in their release line immediately, or downgrade to stable 14.x if on specific canary versions.

### PoC Credit

- The presenter credits Moritz Sanft (msanft) for publishing the initial write-up and working Proof of Concept (PoC).

![Screenshot at 00:02: The video displays the Wiz blog post titled "React2Shell \(CVE-2025-55182\): Everything You Need to Know About the Critical React Vulnerability," setting the context for the technical discussion on the remote code execution flaw.](https://ss.rapidrecap.app/screens/s81dVUM-cQM/00-00-02.png)
![Screenshot at 00:10: A terminal showing a Next.js development server running \(next dev\) and a right-hand terminal running a Python proof-of-concept script targeting localhost:3000.](https://ss.rapidrecap.app/screens/s81dVUM-cQM/00-00-10.png)
![Screenshot at 01:14: A simple diagram drawn in Excalidraw illustrating the standard architecture: Database, Backend, Frontend, and Browser components, showing communication flow.](https://ss.rapidrecap.app/screens/s81dVUM-cQM/00-01-14.png)
![Screenshot at 03:51: The presenter navigates to Moritz Sanft's GitHub profile, highlighting the repository CVE-2025-55182 which contains the explanation and PoC.](https://ss.rapidrecap.app/screens/s81dVUM-cQM/00-03-51.png)
![Screenshot at 06:24: A section of the GitHub README detailing the payload structure used to exploit the vulnerability, specifically showing how \_\_proto\_\_:constructor is used to gain access to the Function constructor.](https://ss.rapidrecap.app/screens/s81dVUM-cQM/00-06-24.png)