MCP Inspector: remote code execution due to missing authentication in MCP Inspector (CVE-2025-49596) #shorts
Summary
Welcome to Security Spotlight. In today’s episode, we unpack CVE-2025-49596, a critical remote code execution vulnerability in the ModelContextProtocol (MCP) Inspector tool. Discovered in June 2025, this flaw allows unauthenticated attackers to execute arbitrary MCP commands, posing a severe risk to developers and organizations relying on MCP servers.
Product details
MCP Inspector is a GitHub-maintained developer utility used for testing and debugging ModelContextProtocol servers. It operates as a client-proxy system over stdio, facilitating live command injection and diagnostics. Versions prior to 0.14.1 of the inspector are affected.
Vulnerability type summary
Classified under CWE-306 (Missing Authentication for Critical Function), this issue stems from a lack of proper authentication between the Inspector client and the proxy. Without an authentication layer, any network or browser-based request can reach into the stdio channel and trigger privileged functions.
Details of the vulnerability
In affected releases (< 0.14.1), the MCP Inspector defines no validation for incoming connections. An attacker only needs network or browser access to the inspector proxy endpoint to send unauthenticated commands. These commands pass directly to the MCP server over stdio, resulting in full remote code execution. Proof-of-concept exploits demonstrate how a simple HTTP request can launch arbitrary diagnostic or control commands, bypassing access controls and compromising the host environment.
Conclusion
To mitigate CVE-2025-49596, immediately upgrade MCP Inspector to version 0.14.1 or later. Developers should verify that authentication is enforced on all proxy endpoints and review audit logs for suspicious command activity. Stay tuned to Security Spotlight for more updates and best practices on safeguarding your development pipelines.
Watch the full video on YouTube: CVE-2025-49596
Remediation and exploitation details
This chain involves the following actors
- Unauthenticated Attacker: Sends malicious requests to the MCP Inspector proxy to trigger remote code execution
This following systems are involved
- MCP Inspector Client (Developer tool for testing and debugging MCP servers): Sends commands over a local proxy without requiring credentials
- Inspector Proxy (Receives commands from the Inspector client and relays them to the MCP server over standard input/output): Executes incoming commands blindly, without verifying the caller’s identity
- MCP Server (Processes Model Context Protocol commands): Executes received commands and returns results
Attack entry point
- Inspector Proxy Interface: Unauthenticated channel on localhost (default TCP port) that accepts MCP command requests from the Inspector client
Remediation actions
Exploitation actions
Port scan or netstat on the developer’s machine
- nmap -p 12345 localhost
HTTP POST or WebSocket frame containing JSON with an MCP 'exec' command
- { "command": "exec", "args": ["/bin/sh -c 'touch /tmp/pwned' "] }
curl or browser-based WebSocket client
- curl -X POST http://localhost:12345/command --data '{...}'
Read stdout/stderr returned via the proxy, or verify side-effects on the host
- ls /tmp | grep pwned
Related Content
NOTE: The following related content has not been vetted and may be unsafe.
- https://github.com/modelcontextprotocol/inspector/security/advisories/GHSA-7f8r-222p-6f5g
- https://github.com/modelcontextprotocol/inspector/commit/50df0e1ec488f3983740b4d28d2a968f12eb8979
- [2025-06-14] A critical vulnerability in modelcontextprotocol inspector up to version 0.14.0 allows for weak authentication exploitation due to an undefined function.
- [2025-07-07] This Week in Security covers Anthropic's vulnerability in the MCP Inspector, CVE-2025-49596, and other security incidents.
- [2025-07-02] Critical RCE vulnerability in Anthropic MCP Inspector allows browser-based exploits.