A severe vulnerability (CVE-2025-49596) has been discovered in Anthropic’s Model Context Protocol (MCP) Inspector, a crucial developer tool for testing and debugging MCP servers. This flaw, carrying a critical CVSS score of 9.4, allows attackers to achieve remote code execution (RCE) on developer machines, potentially top to data theft, backdoor installations, and lateral movement across networks.
The vulnerability primarily affects MCP Inspector versions below 0.14.1 and stems from a lack of authentication between the Inspector client and its proxy. This absence of proper security measures enables unauthenticated requests to trigger arbitrary MCP commands via standard input/output. Exploiting this, attackers can craft malicious websites that, when visited by a developer running the vulnerable MCP Inspector, send requests to localhost services. This bypasses typical browser security controls, including those intended for the 0.0.0.0 IP address, often mistakenly assumed to be secure.
Security researchers highlight that this is one of the first critical RCEs identified within the Anthropic MCP ecosystem, opening a new class of browser-based attacks against AI development tools. The implications are significant for AI teams, open-source projects, and enterprises reliant on MCP, as a successful exploit grants attackers full control over the compromised machine. This includes the ability to exfiltrate sensitive data, install persistent backdoors, and navigate further into connected systems.
While Anthropic has released version 0.14.1 of the MCP Inspector to address these vulnerabilities by adding a session token to the proxy server and incorporating origin validation, concerns remain. An older, but equally impactful, SQL injection vulnerability in Anthropic’s reference SQLite MCP server (forked over 5,000 times before being archived) remains unpatched by Anthropic, as it considers the archived repository “out of scope.” This older flaw could enable stored-prompt injection attacks, manipulating AI agents to execute privileged actions.
Developers are urged to immediately upgrade their MCP Inspector to version 0.14.1 or later. Furthermore, organizations should review their use of any archived Anthropic MCP server implementations and implement manual fixes as recommended by security researchers, such as replacing f-strings with parameterized queries to prevent SQL injection. The incidents underscore the critical need for robust security practices in the rapidly evolving AI development landscape, especially concerning developer tools that interact with local systems.
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