CVE-2025-49596: Remote Code Execution in Anthropic’s MCP Inspector

CVE ID: CVE-2025-49596
Severity: Critical (CVSS 9.8)
Status: Patched
Affected Component: Anthropic’s MCP Inspector
Discovery Date: January 2025

Vulnerability Summary

Remote Code Execution (RCE) vulnerability in Anthropic’s MCP Inspector tool allowing attackers to execute arbitrary code on systems running the inspector through malicious MCP server responses.

Technical Details

Vulnerability Description

The MCP Inspector contains an input validation flaw that allows malicious MCP servers to inject and execute arbitrary code during the inspection process. The vulnerability occurs when the inspector processes server responses without proper sanitization.

Attack Vector

  • Attack Type: Remote Code Execution
  • Access Required: Network access to MCP Inspector
  • User Interaction: Required (user must inspect malicious server)
  • Scope: Changed (can affect other system components)

Affected Versions

  • MCP Inspector versions prior to 1.2.3
  • All versions released before January 15, 2025

Impact Assessment

Potential Impact

  • System Compromise: Complete system takeover possible
  • Data Exfiltration: Access to sensitive data and credentials
  • Lateral Movement: Potential for network-wide compromise
  • Supply Chain Risk: Compromise of development environments

Exploitation Scenarios

  1. Malicious Server Response: Attacker creates malicious MCP server that returns crafted responses
  2. Inspector Execution: Victim uses MCP Inspector to analyze the malicious server
  3. Code Execution: Malicious payload executes with inspector privileges
  4. System Compromise: Attacker gains control of the system

Proof of Concept

Vulnerable Code Pattern

# Vulnerable MCP Inspector code (simplified)
def inspect_server_response(response):
    # Insufficient input validation
    if response.get('type') == 'tool_list':
        tools = response.get('tools', [])
        
        for tool in tools:
            # Dangerous: evaluating user input
            tool_info = eval(tool.get('metadata', '{}'))
            
            # Process tool information
            process_tool_info(tool_info)

Exploit Payload

{
  "type": "tool_list",
  "tools": [
    {
      "name": "legitimate_tool",
      "metadata": "__import__('os').system('whoami')"
    }
  ]
}

Mitigation and Remediation

Immediate Actions

  1. Update MCP Inspector: Upgrade to version 1.2.3 or later
  2. Restrict Access: Limit inspector usage to trusted servers only
  3. Network Isolation: Run inspector in isolated environment
  4. Monitor Activity: Watch for suspicious inspector behavior

Long-term Solutions

  1. Input Validation: Implement comprehensive input sanitization
  2. Sandboxing: Run inspector in sandboxed environment
  3. Principle of Least Privilege: Limit inspector permissions
  4. Security Testing: Regular security assessment of tools

Detection Methods

Indicators of Compromise

  • Unexpected process execution from inspector directory
  • Network connections to suspicious external hosts
  • Unusual system resource usage during inspection
  • Modified system files or configurations

Monitoring Recommendations

# Monitor inspector process activity
ps aux | grep mcp-inspector

# Check for unusual network connections
netstat -an | grep :8080

# Monitor file system changes
find /tmp -name "*.py" -mtime -1

# Check system logs for suspicious activity
grep "mcp-inspector" /var/log/syslog

Vendor Response

Timeline

  • January 10, 2025: Vulnerability discovered and reported
  • January 12, 2025: Anthropic acknowledges vulnerability
  • January 15, 2025: Patch released (version 1.2.3)
  • January 20, 2025: Public disclosure and CVE assignment

Patch Information

  • Fixed Version: MCP Inspector 1.2.3
  • Patch Description: Implemented proper input validation and sandboxing
  • Availability: Available through standard update channels

References and Resources

Official Sources

  • Anthropic Security Advisory: [Link to advisory]
  • CVE Database Entry: [Link to CVE details]
  • Patch Release Notes: [Link to release notes]

Community Resources

  • Security Research: [Link to security research]
  • Detection Rules: [Link to detection rules]
  • Mitigation Guidelines: [Link to guidelines]

This vulnerability demonstrates the critical importance of input validation and sandboxing in MCP tool development and deployment.