Interpretation Conflict

Overview Affected versions of this package are vulnerable to Interpretation Conflict in the JSON-RPC and MCP protocol message parsing. An attacker can bypass intermediary inspection or cause cross-implementation inconsistencies by sending protocol messages with non-standard field casing or Unicod...

CVE-2026-27896

The Go MCP SDK used Go's standard encoding/json.Unmarshal for JSON-RPC and MCP protocol message parsing in versions prior to 1.3.1. Go's standard library performs case-insensitive matching of JSON keys to struct field tags — a field tagged json:"method" would also match "Method", "METHOD", etc...