GHSA-WVJ2-96WP-FQ3F MCP Go SDK Vulnerable to Improper Handling of Case Sensitivity

The Go MCP SDK used Go's standard encoding/json.Unmarshal for JSON-RPC and MCP protocol message parsing. 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. Additionally, Go's standard...

CVE-2026-27896

The CVE-2026-27896 concerns the Go MCP SDK, affected in versions prior to 1.3.1, where Go’s json.Unmarshal (case-insensitive field matching) could accept non-standard JSON-RPC/MCP field casing. This violates JSON-RPC 2.0’s exact field names and could allow messages to bypass intermediary inspecti...