CVE-2026-111770
Published:October 20, 2026
Updated:October 21, 2026
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.
Affected Packages
https://github.com/modelcontextprotocol/typescript-sdk.git (GITHUB):
Affected version(s) >=@modelcontextprotocol/server@2.0.0-alpha.1 <@modelcontextprotocol/server@2.3.0Fix Suggestion:
Update to version @modelcontextprotocol/server@2.3.0https://github.com/modelcontextprotocol/typescript-sdk.git (GITHUB):
Affected version(s) >=v2.0.0-beta.1 <v2.3.0Fix Suggestion:
Update to version v2.3.0@modelcontextprotocol/server (NPM):
Affected version(s) >=2.0.0 <2.3.0Fix Suggestion:
Update to version 2.3.0Related Resources (4)
Do you need more information?
Contact UsCVSS v4
Base Score:
8.4
Attack Vector
NETWORK
Attack Complexity
HIGH
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
LOW
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
7.7
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
LOW
Availability
HIGH
Weakness Type (CWE)
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')