CVE-2026-65831ArcadeDB is a Multi-Model DBMS. Prior to 26.7.1, a reader-role user can submit POST /api/v1/command/{database} with language: js because PolyglotQueryEngine.command, PolyglotQueryEngine.analyze, and PolyglotQueryEngine.registerFunctions do not enforce database-administrator authorization. GraalPolyglotEngine also permits scripts to bypass the allowedPackages whitelist by reflecting from the bound database object through database.getClass().getClassLoader().loadClass to arbitrary host classes. These cooperating defects allow a read-only database user to read arbitrary host files outside the database scope. Process creation is already blocked, so OS command execution is not confirmed. The issue is distinct from CVE-2026-44221, CVE-2026-54076, and CVE-2026-54077. This issue is fixed in version 26.7.1.