Netty is a network application framework for development of protocol servers and clients. Prior to version 4.2.15.Final, the default configuration of the "Http3ConnectionHandler" in the Netty HTTP/3 codec lacks an enforced maximum header size limit. When a peer does not explicitly specify "HTTP3_SETTINGS_MAX_FIELD_SECTION_SIZE", the implementation defaults to an unbounded limit. This insecure default configuration allows a malicious client or server to send an enormous number of headers, leading to a memory exhaustion Denial of Service via an "OutOfMemoryError". Version 4.2.15.Final contains a patch.