MCP Watch has a Critical Command Injection in cloneRepo allows Remote Code Execution (RCE) via malicious URL

Summary

The MCPScanner class contains a critical Command Injection vulnerability in the cloneRepomethod. The application passes the user-supplied githubUrl argument directly to a system shell via execSync without sanitization. This allows an attacker to execute arbitrary commands on the host machine by appending shell metacharacters to the URL.

Details

The vulnerability exists in the src/scanner/MCPScanner.ts file within the cloneRepo method.

https://github.com/kapilduraphe/mcp-watch/blob/0fca7228bd313ae5aa938d61311377e88ce6e682/src/scanner/McpScanner.ts#L181

The code uses child_process.execSync to execute a git clone command:

Because execSync spawns a shell (defaulting to /bin/sh on Unix orcmd.exe on Windows), any shell metacharacters present in the url argument will be interpreted by the shell. The application does not validate that the url is a valid Git URL, nor does it sanitize input for shell metacharacters.

PoC

Install the package or clone the repository.

Run the scanner using the CLI (or invoke scanRepository programmatically).

Provide a malicious URL containing a command separator (e.g., ;, &, or |) and a system command.
payload : npm run scan:github "https://github.com/kapilduraphe/mcp-watch & calc.exe"

<img width="1918" height="1046" alt="image" src="https://github.com/user-attachments/assets/021c1dfa-3f87-483c-aecb-6939bcf9c925" />

Impact

Severity: Critical

CVSS Score: 9.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)
Description: This vulnerability allows an attacker to execute arbitrary code on the machine running the scanner.

If run by a developer locally, it compromises their workstation.

If deployed as a hosted scanning service, it grants the attacker full control over the server (RCE), leading to potential data exfiltration, service disruption, or further lateral movement within the infrastructure.

Context Dependent Risk:

Local CLI : If you run this tool locally on your own machine, you are "hacking yourself." The risk is limited unless you copy-paste a malicious URL sent by someone else (e.g., "Hey, check this repo scan: npm run scan "https://git./..; rm -rf /").

Web Service / CI Pipeline (Critical Risk): If this scanner is deployed as a web service (e.g., "Paste your repo URL to scan"), an attacker can take full control of the server immediately.