In Eclipse Vert.x versions [4.0.0, 4.5.34] or [5.0.0,5.0.12] or [5.1.0,5.1.9] or [5.2.0, 5.2.0], the uniqueItems keyword validation uses an O(n²) pairwise comparison loop with no short-circuit or size limit. A remote unauthenticated attacker can submit a moderately-sized JSON array that consumes disproportionate CPU time, leading to denial of service. The impacted component is io.vertx:vertx-json-schema. The following Vert.x modules depend on vertx-json-schema and are also affected: io.vertx:vertx-web-openapi-router io.vertx:vertx-web-validation io.vertx:vertx-openapi