PT-2026-120314 · Npm · @Modelcontextprotocol/Server
تاريخ النشر
2026-10-20
·
تاريخ التحديث
2026-10-20
CVSS v3.1
7.7
عالية
| المتجه | AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:H |
Summary
In affected versions, an MCP server reached over HTTP could deliver one client's responses and notifications to another client. This happened when clients shared one stateless transport, or one
McpServer or Server instance.Messages were matched to a connection by JSON-RPC
id alone. SDK clients number requests from 0, so ids collide in normal use.Am I affected?
Yes, if more than one client can reach your HTTP endpoint and your code creates the transport or the server once at startup, instead of once per request or per session. Until this release, the README examples of
@modelcontextprotocol/hono, express, fastify and node showed that pattern.Affected versions:
@modelcontextprotocol/server 2.0.0 through 2.2.0.Not affected:
createMcpHandler()with a factory that builds a new server on every call- stdio servers
@modelcontextprotocol/sdk1.26.0 and later
Fix
Upgrade to
@modelcontextprotocol/server 2.3.0 or later.You also need to change your code. The SDK now refuses to be shared, so an affected app fails requests after upgrading: a second
connect() rejects with ALREADY CONNECTED, and a stateless transport rejects its second request.Change to one of these:
createMcpHandler(): pass a factory that builds a newMcpServeron every call.- Per request: build a new
McpServerand a new transport inside the request handler. - Per session: set
sessionIdGeneratorand keep oneMcpServerand one transport per session.
If you cannot upgrade yet, the same change fixes affected versions.
إصلاح
Race Condition
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المنتجات المتأثرة
@Modelcontextprotocol/Server