LiteLLM MCP Auth Bypass Attempt - Malformed Single-Character Bearer Token to /mcp/

Arnold Chan@slaz

•updated Sep 12, 2026•0•0•1

Detects a multi-stage authentication bypass attempt against LiteLLM MCP endpoints. The rule tracks an initial malformed Authorization Bearer token request to the /mcp/ endpoint, followed by a server response returning a 200 OK status code accompanied by an 'mcp-session-id' header, confirming the exploitation of CVE-2026-59822.