CVE-2026-52869 | BDVDB-2026-348652 Detail
modelcontextprotocolpython-sdk
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.
Impact#
Per CVSS v3.1: confidentiality impact high, integrity impact high, availability impact low. Attack vector: network.
Weaknesses#
- CWE-639 Authorization Bypass Through User-Controlled Key
References#
- https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-jpw9-pfvf-9f58
- https://github.com/modelcontextprotocol/python-sdk/pull/2690
- https://github.com/modelcontextprotocol/python-sdk/pull/2719
- https://github.com/modelcontextprotocol/python-sdk/commit/1abcca2408a6b50e10ec601181f63f9978705c00
- https://github.com/modelcontextprotocol/python-sdk/commit/ce267b6fc515dc4efc1dc70b6975b16ff0feef0a
- https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2
Exploit#
No public exploit known
History#
- Version 1Record published in the CVE List.
- Version 2Most recent update recorded in the CVE List.