CVE-2026-111771
Published:October 20, 2026
Updated:October 21, 2026
In affected versions, the SDK's server-side bearer authentication had no way to check that a token was issued for your server (its audience). Where one authorization server issues tokens for several services, a valid token for another service was also accepted by your MCP server.
Affected Packages
https://github.com/modelcontextprotocol/typescript-sdk.git (GITHUB):
Affected version(s) >=@modelcontextprotocol/server@2.0.0-beta.3 <@modelcontextprotocol/server@2.3.0Fix Suggestion:
Update to version @modelcontextprotocol/server@2.3.0https://github.com/modelcontextprotocol/typescript-sdk.git (GITHUB):
Affected version(s) >=@modelcontextprotocol/express@2.0.0-alpha.4 <@modelcontextprotocol/express@2.0.2Fix Suggestion:
Update to version @modelcontextprotocol/express@2.0.2https://github.com/modelcontextprotocol/typescript-sdk.git (GITHUB):
Affected version(s) >=v2.0.0-beta.1 <v2.3.1Fix Suggestion:
Update to version v2.3.1https://github.com/modelcontextprotocol/typescript-sdk.git (GITHUB):
Affected version(s) >=1.6.0 <1.32.0Fix Suggestion:
Update to version 1.32.0https://github.com/modelcontextprotocol/typescript-sdk.git (GITHUB):
Affected version(s) >=@modelcontextprotocol/server-legacy@2.0.0-alpha.3 <@modelcontextprotocol/server-legacy@2.3.1Fix Suggestion:
Update to version @modelcontextprotocol/server-legacy@2.3.1@modelcontextprotocol/sdk (NPM):
Affected version(s) >=1.6.0 <1.32.0Fix Suggestion:
Update to version 1.32.0@modelcontextprotocol/server (NPM):
Affected version(s) >=2.0.0 <2.3.0Fix Suggestion:
Update to version 2.3.0@modelcontextprotocol/express (NPM):
Affected version(s) >=2.0.0 <2.0.2Fix Suggestion:
Update to version 2.0.2@modelcontextprotocol/server-legacy (NPM):
Affected version(s) >=2.0.0 <2.3.1Fix Suggestion:
Update to version 2.3.1Related Resources (5)
Do you need more information?
Contact UsCVSS v4
Base Score:
7.6
Attack Vector
NETWORK
Attack Complexity
HIGH
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
NONE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
HIGH
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
6.8
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
NONE
Weakness Type (CWE)
Incorrect Authorization