CVE-2026-33252
March 23, 2026
The Go MCP SDK used Go's standard encoding/json. Prior to version 1.4.1, the Go SDK's Streamable HTTP transport accepted browser-generated cross-site "POST" requests without validating the "Origin" header and without requiring "Content-Type: application/json". In deployments without Authorization, especially stateless or sessionless configurations, this allows an arbitrary website to send MCP requests to a local server and potentially trigger tool execution. Version 1.4.1 contains a patch for the issue.
Affected Packages
https://github.com/modelcontextprotocol/go-sdk.git (GITHUB):
Affected version(s) >=v0.1.0 <v1.4.1Fix Suggestion:
Update to version v1.4.1github.com/modelcontextprotocol/go-sdk (GO):
Affected version(s) >=v0.0.0-20250604145159-a07ce11b3700 <v1.4.1Fix Suggestion:
Update to version v1.4.1Related Resources (4)
Do you need more information?
Contact UsCVSS v4
Base Score:
7.1
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
PASSIVE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
HIGH
Vulnerable System Availability
LOW
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
7.1
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
NONE
Integrity
HIGH
Availability
LOW
Weakness Type (CWE)
Cross-Site Request Forgery (CSRF)
EPSS
Base Score:
0.01
