Executive Summary

Wiz Research discovered a high-severity vulnerability in Amazon Q Developer Extension for Visual Studio Code (VS Code), Amazon's AI-powered coding assistant for VS Code, which allowed attackers to achieve arbitrary code execution and cloud credential theft simply by having a developer open a malicious repository. Amazon Q automatically loaded MCP server configurations from workspace files without user consent. Combined with full environment inheritance, this enabled immediate code execution. 

Amazon has remediated this issue in language server version 1.65.0.

This vulnerability is part of a broader pattern affecting AI coding tools. Similar issues have been independently discovered across the ecosystem - including findings by OX Security and Check Point published around the same time - demonstrating that MCP auto-execution is a systemic risk requiring industry-wide attention.

Introduction

AI-powered coding assistants have become essential tools for developers. Extensions like Amazon Q, GitHub Copilot, and others integrate deeply into our development environments, offering code suggestions, automated refactoring, and intelligent tooling. To enable richer functionality, many of these tools have adopted the Model Context Protocol (MCP) - a standard that allows AI assistants to spawn local processes and interact with external services.

This post details a vulnerability discovered in the Amazon Q VS Code extension where MCP server configurations were automatically loaded and executed from workspace files - without user consent. The result: opening a malicious repository could lead to immediate code execution - with full access to the developer's environment, including cloud credentials, API keys, and internal systems.

The Trust Boundary Problem

When you open a project folder in VS Code, you're implicitly trusting dozens of configuration files: package.json, .vscode/settings.json, .eslintrc, and many others. Most of these are declarative - they configure behavior but don't execute code directly.

Extensions, however, often blur this line. They may read workspace-specific configs and act on them automatically. The critical question becomes: what happens when an attacker controls those config files?

The result: a developer clones a seemingly legitimate repository, opens it in their IDE, and malicious configs execute before they've reviewed a single line of code.

MCP: Power and Peril

The Model Context Protocol enables AI assistants to spawn local processes called "MCP servers". These servers extend the AI's capabilities - connecting to databases, calling APIs, running build tools, or accessing local resources.

A typical MCP configuration looks like this:

The security model assumes the user explicitly configures these servers. After all, you're granting an AI assistant permission to run arbitrary commands on your machine. This should require informed consent.

The vulnerability arose when this assumption was violated: Amazon Q automatically loaded MCP configurations from .amazonq/mcp.json within the workspace - no prompt, no consent, no workspace trust check.

Technical Breakdown

The vulnerability stemmed from two behaviors in how Amazon Q handled MCP server configurations:

Problem 1: Auto-execution without consent

The extension loaded .amazonq/mcp.json from the workspace root immediately upon opening the folder. No dialog asked the user to approve these MCP servers. No workspace trust check prevented execution in untrusted folders.

Problem 2: Full environment access

Spawned processes inherited the user's complete environment. For developers working with cloud services, this typically includes: 

• AWS credentials (AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_SESSION_TOKEN)

• Cloud CLI authentication tokens

• API keys and secrets

• SSH agent sockets

The combination meant that a single malicious config file could execute arbitrary commands with full access to the developer's credentials - no user interaction required beyond opening the folder and activating Amazon Q.

Proof of Concept

To demonstrate the vulnerability, we created a minimal malicious repository:

The mcp.json contained:

Attack flow:

1. Victim clones the repository (perhaps a typosquatted package or malicious PR).

2. Victim opens the folder in VS Code with Amazon Q installed.

3. When the victim activates Amazon Q, the extension loads and executes the malicious MCP configuration - without prompting for consent.

4. The attacker's payload runs with access to the victim's AWS credentials.

In our testing, the aws sts get-caller-identity command successfully captured the developer's active AWS session - demonstrating how an attacker could escalate from code execution to cloud compromise.

Impact Assessment

Immediate Impact:

• Arbitrary code execution on the victim's machine

• Minimal user interaction required - opening the folder with Amazon Q active

• Silent execution with no visible indicators

Escalation Potential:

• Theft of cloud credentials (AWS, GCP, Azure)

• Cloud persistence - backdoor IAM users, access keys, or infrastructure

• Access to internal services via inherited VPN/network context

• Supply chain attacks targeting maintainers of popular projects

• Lateral movement if the developer has access to production systems

Attack Scenarios:

• Malicious pull request to a popular repository

• Typosquatted package names

• Compromised dependencies with added config files

• Social engineering - fake job interviews (a known DPRK tactic) where candidates are asked to clone and run "coding tests"

Part of a Broader Pattern

This vulnerability is not unique to Amazon Q. The pattern of auto-executing workspace configurations without consent has been discovered repeatedly across the VS Code ecosystem and AI coding tools. Notable related findings include:

Broader Security Lessons

Lesson 1: Workspace Configs Are Attacker-Controlled Input

Any file that can exist in a git repository should be treated as untrusted input. Extensions must validate, sanitize, and - most importantly - obtain consent before acting on workspace configs.

Lesson 2: Convenience Features Often Skip Consent

The auto-loading behavior was likely designed for convenience. But convenience and security are often in tension. The safest default is to require explicit consent for any action that executes code. VS Code's workspace trust feature exists precisely for this reason - extensions should integrate with it.

Lesson 3: Environment Inheritance Is an Underrated Risk

When spawning child processes, inheriting the full environment is the path of least resistance. But it's also a significant security risk. Processes should receive the minimum environment necessary. This is especially critical for AI coding tools where developers work while authenticated to cloud services.

Required Actions and Mitigations

Amazon has remediated this issue. No immediate action is required for users on language server version 1.65.0 or later.

However, we recommend developers take the following precautions:

• Be cautious with untrusted repositories - Treat unfamiliar projects with care.

• Review MCP consent prompts carefully - When Amazon Q displays an "Untrusted MCP Server" warning, inspect the command before allowing.

• Review workspace directories - Check for unexpected .amazonq/ folders in repositories.

• Audit MCP configurations - Review any MCP server configurations in your environment.

Amazon Q now displays a consent prompt before loading MCP servers from workspace configurations, giving users the opportunity to review and reject untrusted commands:

AWS Public Statement

“We would like to thank Wiz for collaborating with us on this issue. We have remediated this issue in language server version 1.65.0.

The AWS Language Server updates automatically unless the customer's network configuration prevents it, so no action is required in most cases. For existing customers, reloading the IDE will trigger an update to the latest language server version, which includes this fix. If auto-update is blocked, we recommend upgrading to the latest version of the Amazon Q Developer plugin for your IDE. New customers require no action, as the latest patched version will be downloaded automatically.

Customers can learn more by reading Security Bulletin 2026-047-AWS”

Responsible Disclosure Timeline

April 17, 2026 - Vulnerability discovered

April 20, 2026 - Initial report submitted to Amazon Security

April 20, 2026 - Amazon acknowledged receipt

May 12, 2026 - Fix deployed via Language Server update, resolving the issue in the Amazon Q VS Code Extension.

June 23, 2026 - CVE-2026-12957 assigned

June 26, 2026 - Public disclosure

Conclusion

The combination of auto-execution, shell spawning, and environment inheritance created a high-severity vulnerability in a widely-used developer tool. A single malicious repository could compromise not just the developer's local machine, but their cloud infrastructure as well.

As AI coding assistants become more powerful and more prevalent, the security community must scrutinize them with the same rigor we apply to browsers, operating systems, and other trusted computing bases. The convenience these tools provide is immense - but so is their potential for abuse.

This vulnerability was discovered by Maor Dokhanian (Wiz) and disclosed responsibly to Amazon. We thank Amazon for their prompt response and collaborative approach to remediation.