AIKIDO-2026-10318
fastmcp is vulnerable to Exposure of Sensitive Information to an Unauthorized Actor
70
High Risk
This Affects:
fastmcpTL;DR
Affected versions of this package leak the MCP transport's Authorization header to downstream third-party APIs when using FastMCP.from_openapi() over Streamable HTTP. The get_http_headers() function does not exclude the authorization header, and request.headers.update() overwrites the API key configured on the httpx client with the MCP client's credentials. The patch adds authorization to the excluded headers set and changes MCP header forwarding to a non-overwriting pattern.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range.
Background info
fastmcp is vulnerable to Exposure of Sensitive Information to an Unauthorized Actor in versions 0.0.1 - 3.0.1.
How to fix this
Upgrade the fastmcp library to the patch version.
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SOC 2Compliant
ISO 27001Compliant