CVEvulnerability
CVE-2026-52869
7.1 HIGH
Official page ↗
- Status
- Analyzed
- Published
- 2026-07-15
- Last modified
- 2026-10-24
- Assigner
- [email protected]
- CVSS 3.1 ([email protected])
- 7.1 HIGH — CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L
- Weaknesses
- CWE-639
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.
Affected configurations
• lfprojects mcp python sdk (< 1.27.2)
Related
Weakness · CWE (1)
- CWE-639 Authorization Bypass Through User-Controlled Key weakness
References
- https://github.com/modelcontextprotocol/python-sdk/commit/1abcca2408a6b50e10ec601181f63f9978705c00 Patch
- https://github.com/modelcontextprotocol/python-sdk/commit/ce267b6fc515dc4efc1dc70b6975b16ff0feef0a Patch
- https://github.com/modelcontextprotocol/python-sdk/pull/2690 Issue Tracking, Patch
- https://github.com/modelcontextprotocol/python-sdk/pull/2719 Issue Tracking, Patch
- https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.27.2 Release Notes
- https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-jpw9-pfvf-9f58 Vendor Advisory