Fast-DDS: Unbounded GAP range triggers OOM DoS under RELIABLE QoS

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.