CVE-2026-47427 affects the GitHub MCP Server prior to version 1.1.0. The vulnerability resides in the CompletionsHandler function in pkg/github/server.go, which accesses params.Ref without first checking for a nil value. A crafted completion/complete JSON-RPC request with a missing or empty ref field triggers a nil pointer dereference, causing a Go runtime panic and complete server crash. The crash occurs before any authentication or token validation, meaning any unauthenticated client with network access to send JSON-RPC messages can exploit this flaw. The result is a complete denial of service condition. No credentials or special privileges are required to trigger the vulnerability. The issue has been patched in GitHub MCP Server version 1.1.0. Users are advised to upgrade immediately to mitigate the risk of unauthenticated denial of service attacks.