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], a gRPC endpoint does have a configurable per message maximum size in bytes, however the maximum size applies to the received bytes. When applied to a compressed message, this only applies to the compressed size and not the actual size of the uncompressed content. This can be used to force a gRPC endpoint to allocate more bytes than the value defined by the configuration, making the endpoint vulnerable to compression bomb attacks.

The impacted component is io.vertx:vertx-gprc-server.