MCP Python SDK: HTTP transports serve session requests without verifying the authenticated principal
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
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| modelcontextprotocol | python-sdk | affected |
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No data.
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| Modelcontextprotocol | Python-sdk |
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| Source | ID | Title |
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Github GHSA |
GHSA-jpw9-pfvf-9f58 | MCP Python SDK: HTTP transports serve session requests without verifying the authenticated principal |
No CVSS v4.0
No CVSS v3.0
No CVSS v2
This CVE is not in the KEV list.
Exploit prediction score: < 1% (0.535% probability within 30 days)
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| Metrics |
ssvc
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| First Time appeared |
Modelcontextprotocol
Modelcontextprotocol python-sdk |
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| Vendors & Products |
Modelcontextprotocol
Modelcontextprotocol python-sdk |
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| 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. | |
| Title | MCP Python SDK: HTTP transports serve session requests without verifying the authenticated principal | |
| Weaknesses | CWE-639 | |
| References |
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| Metrics |
cvssV3_1
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