MCP Python SDK: Unbounded Session Accumulation in StreamableHTTP Transport Enables Resource Exhaustion

Summary In affected versions, a Streamable HTTP server in stateful mode the default never reclaimed session state: - sessions did not expire; - a client DELETE ended the session but left its entry registered; - a session whose first request was refused stayed registered with a running task. Each...

GHSA-84M7-P3X7-PCFV MCP Python SDK: Unbounded Session Accumulation in StreamableHTTP Transport Enables Resource Exhaustion

Summary In affected versions, a Streamable HTTP server in stateful mode the default never reclaimed session state: - sessions did not expire; - a client DELETE ended the session but left its entry registered; - a session whose first request was refused stayed registered with a running task. Each...

CVE-2026-59951

A flaw was found in the Model Context Protocol MCP Python SDK. Stateful streamable HTTP servers fail to enforce idle session expiration or limits on active sessions, preventing terminated or rejected requests from releasing their resources. A remote attacker can exploit this issue by repeatedly...

CVE-2026-59951

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol MCP. From 1.8.0 until 1.30.0 and 2.2.0, stateful Streamable HTTP servers, including FastMCP, MCPServer, Server.streamablehttpapp, and StreamableHTTPSessionManager, retain session entries without an id...

CVE-2026-59951

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol MCP. From 1.8.0 until 1.30.0 and 2.2.0, stateful Streamable HTTP servers, including FastMCP, MCPServer, Server.streamablehttpapp, and StreamableHTTPSessionManager, retain session entries without an id...

CVE-2026-59951 MCP Python SDK: Unbounded Session Accumulation in StreamableHTTP Transport Enables Resource Exhaustion

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol MCP. From 1.8.0 until 1.30.0 and 2.2.0, stateful Streamable HTTP servers, including FastMCP, MCPServer, Server.streamablehttpapp, and StreamableHTTPSessionManager, retain session entries without an id...

CVE-2026-59951 MCP Python SDK: Unbounded Session Accumulation in StreamableHTTP Transport Enables Resource Exhaustion

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol MCP. From 1.8.0 until 1.30.0 and 2.2.0, stateful Streamable HTTP servers, including FastMCP, MCPServer, Server.streamablehttpapp, and StreamableHTTPSessionManager, retain session entries without an id...

CVE-2026-59951

The MCP Python SDK (PyPI: mcp) versions 1.8.0 through 1.30.0 and 2.2.0 are vulnerable to unbounded session accumulation within the StreamableHTTP transport . Specifically, stateful servers—including FastMCP , MCPServer , Server.streamable_http_app() , and StreamableHTTPSessionManager —fail to exp...

CVE-2026-59951: Uncontrolled Resource Consumption

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol MCP. From 1.8.0 until 1.30.0 and 2.2.0, stateful Streamable HTTP servers, including FastMCP, MCPServer, Server.streamablehttpapp, and StreamableHTTPSessionManager, retain session entries without an id...

Official MCP Python SDK Flaw Can Let Malicious Servers Steal OAuth Credentials

A malicious MCP server could trick an application built on the official MCP Python SDK into handing over the OAuth credentials it uses to log in to a real service, the SDK's maintainers said in a security advisory. Affected versions sent the client secret, the authorization code, and the PKCE pro...

Security Bulletin: Multiple security vulnerabilities have been identified in Python packages shipped with IBM Guardium Cryptography Manager (GCM)

Summary Multiple security vulnerabilities identified in Python packages shipped with IBM Guardium Cryptography Manager GCM have been addressed Vulnerability Details CVEID:CVE-2026-48775 DESCRIPTION: LangGraph SQLite Checkpoint is an implementation of LangGraph CheckpointSaver that uses SQLite DB...

CVE-2026-52870

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol MCP. From 1.23.0 until 1.27.2, default handlers installed by server.experimental.enabletasks for tasks/list, tasks/get, tasks/result, and tasks/cancel operate only on task identifiers without recordin...

CVE-2026-59950

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol MCP. Prior to 1.28.1, the deprecated mcp.server.websocket.websocketserver transport accepted WebSocket handshakes without applying Host or Origin header validation, leaving no SDK-level way to restric...

CVE-2026-59950

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol MCP. Prior to 1.28.1, the deprecated mcp.server.websocket.websocketserver transport accepted WebSocket handshakes without applying Host or Origin header validation, leaving no SDK-level way to restric...

CVE-2026-59950

The MCP Python SDK (package name mcp on PyPI) contains a vulnerability in the deprecated mcp.server.websocket.websocket_server transport prior to version 1.28.1, which accepted WebSocket handshakes without Host or Origin header validation. This prevents restrictions on originating connections to ...

CVE-2026-52870

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol MCP. From 1.23.0 until 1.27.2, default handlers installed by server.experimental.enabletasks for tasks/list, tasks/get, tasks/result, and tasks/cancel operate only on task identifiers without recordin...

CVE-2026-52870

The MCP Python SDK (package mcp on PyPI) has a vulnerability in versions 1.23.0–1.27.1 where default handlers installed by server.experimental.enable_tasks() for tasks/list, tasks/get, tasks/result, and tasks/cancel only operate on task identifiers and do not record the session that created each ...

CVE-2026-52869 MCP Python SDK: HTTP transports serve session requests without verifying the authenticated principal

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol MCP. Prior to 1.27.2, the SSE and stateful Streamable HTTP transports mcp.server.sse.SseServerTransport and mcp.server.streamablehttpmanager.StreamableHTTPSessionManager route requests to existing...

CVE-2026-59950: Origin Validation Error

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol MCP. Prior to 1.28.1, the deprecated mcp.server.websocket.websocketserver transport accepted WebSocket handshakes without applying Host or Origin header validation, leaving no SDK-level way to restric...

CVE-2026-52869: Authorization Bypass Through User-Controlled Key

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol MCP. Prior to 1.27.2, the SSE and stateful Streamable HTTP transports mcp.server.sse.SseServerTransport and mcp.server.streamablehttpmanager.StreamableHTTPSessionManager route requests to existing...