6.5
Medium
CVE-2026-116686 The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients
Description
The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients. From 1.10.0 until 1.30.0 and 2.2.0, ClientSession, ClientSessionGroup, and Client tool calls validate server-declared outputSchema documents with jsonschema's default resolver, causing an unresolved $ref value to fetch an HTTP, HTTPS, or file URL from the client's network and filesystem context. A server can trigger blind requests or local-file reads and can stall every session in the process because resolution runs synchronously on the event loop without a timeout. This issue is fixed in versions 1.30.0 and 2.2.0.
Affected products and versions
| Product | Affected versions | Fixed in |
|---|---|---|
| python-sdk 2.0 | 2.0.0 → < 2.2.0 | 2.2.0 |
| python-sdk 1.10 | 1.10.0 → < 1.30.0 | 1.30.0 |
References
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com
Timeline
- Published
- Last modified
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CVE-2026-116684
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CVE-2026-109527
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CVE-2026-59951
The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP)
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