Summary

Generation of Error Message Containing Sensitive Information vulnerability in ash-project ashai allows a caller of an AshAi tool to read internal error details, including module names and data values, by making a tool call fail.

AshAi.ToToolError gained an implementation for Ash.Error.Unknown.UnknownError that returns the error's error field as is, and AshAi.Tool.Errors.format/1 sends that text to MCP clients (tool calls and resource reads in AshAi.Mcp.Server) and to the model in AshAi.ToolLoop. Ash stores the full Exception.format/2 output of a raised exception, or inspect/1 of a bare {:error, term} return, in that field. A tool result that cannot be JSON-encoded raises a Protocol.UndefinedError whose text includes the inspected value, which can be a whole record with fields the tool never returns. None of these errors were logged. The fix logs them under an error id and returns only that id to the caller.

This issue affects ashai: from 1.5.0 before 1.5.1.

Impact

A caller with tool access sends unexpected or malformed tool arguments until a tool fails, then reads the returned error text to learn internal module and function names and the values the code failed on.