AIKIDO-2026-890125

mcp is vulnerable to Information Exposure Through an Error Message

Information Exposure Through an Error Message Pre-CVE Published 2 days ago

Medium Risk

This Affects:

mcp

0.1.0 - 1.1.0

Fixed in 1.2.0

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TL;DR

The MCP server places raw internal exception messages into the data field of JSON-RPC error responses returned to clients. Because these messages are sent to untrusted callers, internal implementation details such as backtraces, class names, file paths, and other state can be disclosed when a request triggers an exception. Any client able to reach the server and cause an error can read this information without authentication. The fix sanitizes exception details before they are placed into JSON-RPC error responses.

Who does this affect?

You are affected if you run an MCP server built on a vulnerable version and it returns JSON-RPC errors to untrusted or externally reachable callers. Any request that triggers a handled exception on the server returns the raw exception message in the JSON-RPC error data field, disclosing internal details (messages, class names, paths) to the caller without authentication.