Fast DDS is a C++ implementation of the DDS (Data Distribution Service) standard of the OMG (Object Management Group ). Prior to versions 3.4.1, 3.3.1, and 2.6.11, a remotely triggerable Out-of-Memory (OOM) denial-of-service exists in Fast -DDS when processing RTPS GAP submessages under RELIABLE QoS. By sending a tiny GAP packet with a huge gap range ("gapList .base - gapStart"), an attacker drives "StatefulReader::processGapMsg()" into an unbounded loop that inserts millions of s equence numbers into "WriterProxy::changes_received_" ("std::set"), causing multi-GB heap growth and process termination. No authentication is required beyond network reachability to the reader on the DDS domain. In environments without an RSS limit (non-ASan / unlimited), memory consumption was observed to rise to ~64 GB. Versions 3.4.1, 3.3.1, and 2.6.11 patch t he issue.