webonyx graphql-php is a PHP implementation of the GraphQL specification. Prior to 15.32.3, GraphQL\Language\Parser performs recursive descent without a recursion limit in parseSelectionSet, parseValueLiteral, and parseTypeReference. A remote attacker can submit deeply nested selection sets, object or list values, or list types that exhaust the PHP process stack during pre-validation parsing, before query validation and complexity controls run. The resulting SIGSEGV can terminate PHP-FPM workers or long-running Swoole, RoadRunner, ReactPHP, or CLI processes and cannot be caught by application-level exception handling. This issue is fixed in version 15.32.3.