CVE-2026-116686
MEDIUM
MEDIUM
Priority: 0.02
BB Relevance:
63/100
Published: 2026-10-27
Modified: 2026-10-28
First seen: 2026-10-29
Status: active
Attack Surface
Network
Low Complexity
No Auth
CVSS Vector Breakdown
AV:
Network
AC:
Low
PR:
None
UI:
Required
S:
Unchanged
C:
None
I:
None
A:
High
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.
Weakness Classification (1)
Affected Software (4)
| Vendor | Product | Version |
|---|---|---|
| modelcontextprotocol | python-sdk | >= 1.10.0, < 1.30.0 |
| modelcontextprotocol | python-sdk | >= 2.0.0, < 2.2.0 |
| modelcontextprotocol | python-sdk | >= 1.10.0, < 1.30.0 |
| modelcontextprotocol | python-sdk | >= 2.0.0, < 2.2.0 |