CVE WatchJul 17, 2026

CVE-2026-52869

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 statefu

CVSS

7.1

High

EPSS

0.3%

p16

KEV

—

Exploit Today

0-100

Published: Jul 15, 2026 · Last modified: Jul 17, 2026 · CWE-639

EPSS · 30d

0.3%EPSS · 30 days0.3%

2026-07-162026-07-20

Technical description

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.streamable_http_manager.StreamableHTTPSessionManager route requests to existing sessions using only the session_id query parameter or Mcp-Session-Id header without verifying the authenticated principal that created the session, allowing a different bearer-token-authenticated client with a known session ID to inject JSON-RPC messages into that session. This issue is fixed in version 1.27.2.

Official references

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