CVE-2025-49596: Critical Flaw in Anthropic’s MCP Inspector Leads to RCE

A critical vulnerability recently uncovered in Anthropic’s MCP Inspector has raised alarms across the AI developer landscape.

Anthropic’s MCP Inspector is a developer tool used for testing and debugging MCP servers – systems that allow AI applications to work with live data and external tools. It consists of a client interface and a proxy server that connects to MCP services.

Identified as CVE-2025-49596, the flaw exposes Anthropic’s MCP Inspector to Remote Code Execution (RCE), potentially granting attackers full control over affected machines.

In this blog, we break down why this vulnerability is so dangerous and what steps you need to take to protect your systems.

What Is CVE-2025-49596?

CVE-2025-49596 (CVSS 9.4) resides in Anthropic’s Model Context Protocol (MCP) Inspector, and is caused by overly lenient security defaults in MCP Inspector.

By default, the proxy server allows unauthenticated connections and lacks encryption, granting it the power to spawn local processes and execute commands. This configuration creates a broad attack surface, especially when the proxy is exposed to untrusted networks, intentionally or otherwise.

Researchers demonstrated that an attacker can chain this vulnerability with a known browser-level flaw, dubbed “0.0.0.0 Day”, and a Cross-Site Request Forgery (CSRF) issue to trigger RCE. In simple terms, a developer just needs to visit a malicious website for the exploit to take effect. The Proof-of-Concept (PoC) exploit also leveraged Server-Sent Events (SSE) to dispatch malicious requests.

It is important to understand that the IP address 0.0.0.0, when used by the proxy, binds the service to all network interfaces, including localhost (127.0.0.1). This means services thought to be isolated can actually be reached via external routes, significantly increasing exposure.

Who and What Is Affected by CVE-2025-49596?

All versions of MCP Inspector released prior to 0.14.1 are vulnerable. Developers can verify their version by running “npm list -g”.Be sure to check both global installations and local project dependencies (in node_modules).

Additionally, anyone running the tool via mcp dev or integrating it into their open-source workflows may be at risk. Organizations that use MCP Inspector as part of their LLM deployment pipelines should treat this vulnerability as a top priority.

How Could It Be Exploited and What’s at Stake?

The attack unfolds via a chain of overlooked configurations and browser quirks. Here’s how it works:

• A malicious website uses CSRF to send commands to the MCP proxy running locally.
• Browsers misinterpret requests to the 0.0.0.0 IP address, exposing local services to remote manipulation.
• The proxy server, running without authentication, processes these commands and executes them.

The result? Arbitrary code execution on the victim’s machine.

Attackers could:

• Steal sensitive credentials or API keys.
• Install persistent backdoors or open reverse shells.
• Escalate privileges and move laterally within connected networks, posing a broader organizational risk.

Even developers who assume localhost-based tools are safe could unknowingly expose themselves, especially when browser behaviors and default network bindings (like 0.0.0.0) come into play.

Keep your security team informed with the latest vulnerability disclosures and real-world exploit trends. SOCRadar’s Cyber Threat Intelligence module provides continuous updates on emerging CVEs and active attacks, helping you prioritize remediation efforts and reduce risk faster. Detect relevant threats quickly and respond with confidence using timely, actionable intelligence.

How to Mitigate CVE-2025-49596

The vulnerability was responsibly disclosed and patched as of June 13, 2025. It was first reported by a researcher on March 26, 2025, with additional disclosures from Oligo Security on April 18. The maintainers addressed the issue in version 0.14.1, released in June.

This update introduces several important security features:

• Session-based authentication between the client and proxy.
• HTTP header validation for Host and Origin fields.
• Default blocking of DNS rebinding and CSRF attempts.

To secure your environment:

1. Upgrade immediately:

npm install -g “@modelcontextprotocol/inspector@^0.14.1”

2. Confirm the update:

npm list -g “@modelcontextprotocol/inspector”

3. Audit network exposure: Ensure that MCP Inspector instances are not accessible from untrusted networks.

For complete technical details and proof-of-concept scenarios, consult the official GitHub advisory or Oligo Security’s detailed report.

Understand your digital footprint inside and out. SOCRadar Attack Surface Management (ASM) continuously discovers and monitors your external assets, identifying exposed vulnerabilities and misconfigurations that matter most to your environment. By focusing on what truly impacts your risk, ASM enables your team to prioritize fixes effectively and strengthen your security posture faster.