Critical RCE Vulnerability in Anthropic MCP Inspector – CVE-2025-49596

> The vulnerability stems from the inability of certain browsers to properly handle the IP address 0.0.0.0, which is often assumed to be secure because it points to localhost. Attackers can exploit this flaw by crafting a malicious website that sends requests to localhost services running on an MCP server, thereby gaining the ability to execute arbitrary commands on a developer’s machine.

The 0.0.0.0-day vulnerability is a 19-year old unpatched bug that exists on many browsers [0] that no-one cared about fixing and it's used to infiltrate local services on the user's machine by visiting any website that fetches from https://0.0.0.0/....

So it is really is not a good idea to have MCP servers and proxies running all over the place on your machine and then you get pwned by going to some random website.

Additionally, including data exfiltration, RCEs, and data leakages the "Model Context Protocol" is really one of the worst standards that has ever been designed.

[0] https://www.oligo.security/blog/0-0-0-0-day-exploiting-local...