The Model Context Protocol has a security warning advising servers to validate the Origin header on all incoming connections to prevent DNS rebinding attacks. Prior to the v0.25.0 release, users had no way to validate the origins host. In v0.25.0, a new –allowed-hosts flag was introduced alongside the existing –allowed-origins flag, enabling users to specify permitted hosts at server startup. Both flags default to *, allowing users to implement strict access controls as needed without breaking existing setups. If either flag is set to *, the server will output a startup warning about potential vulnerabilities. Documentation has also been updated to highlight these security considerations.
Weakness
The product does not properly verify that the source of data or communication is valid.
Related Attack Patterns
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