MCP SDKs security advisories

9 advisories · 7 critical or high in 12 months · latest Jul 16

9 advisories

Date	Advisory	Severity	Fixed in
Jul 16	MCP Python SDK: WebSocket server transport does not support Host/Origin validation CVE-2026-59950Highfixed in 1.28.1	High	1.28.1
Jul 16	MCP Python SDK: HTTP transports serve session requests without verifying the authenticated principal CVE-2026-52869High7.1fixed in 1.27.2	High7.1	1.27.2
Jul 16	MCP Python SDK: Experimental task handlers allow any client to access and cancel other clients' tasks CVE-2026-52870High7.6fixed in 1.27.2	High7.6	1.27.2
Feb 4	@modelcontextprotocol/sdk has cross-client data leak via shared server/transport instance reuse CVE-2026-25536High7.1fixed in 1.26.0	High7.1	1.26.0
Jan 5	Anthropic's MCP TypeScript SDK has a ReDoS vulnerability CVE-2026-0621Highfixed in 1.25.2	High	1.25.2
Dec 22025	Model Context Protocol (MCP) Python SDK does not enable DNS rebinding protection by default CVE-2025-66416Highfixed in 1.23.0	High	1.23.0
Dec 22025	Model Context Protocol (MCP) TypeScript SDK does not enable DNS rebinding protection by default CVE-2025-66414Highfixed in 1.24.0	High	1.24.0
Jul 42025	MCP Python SDK vulnerability in the FastMCP Server causes validation error, leading to DoS CVE-2025-53366Highfixed in 1.9.4	High	1.9.4
Jul 42025	MCP Python SDK has Unhandled Exception in Streamable HTTP Transport, Leading to Denial of Service CVE-2025-53365Highfixed in 1.10.0	High	1.10.0

About MCP SDKs

The Model Context Protocol SDKs for Python and TypeScript.

Packages watched: mcp (PyPI), @modelcontextprotocol/sdk (npm).

modelcontextprotocol/python-sdk

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