eprosima Fast DDS is a C++ implementation of the DDS (Data Distribution Service) standard of the OMG (Object Management Group). Versions prior to 2.6.12, 2.14.6, 3.2.4, 3.3.1, and 3.4.2 have a remotely triggerable Out-of-Bounds Read while processing RTPS DATA_FRAG submessages. An attacker can craft a DATA_FRAG with a large sampleSize but a small actual payload, and set fragmentsInSubmessage such that the receiver treats the packet as the LAST fragment**. In this LAST-fragment path, Fast-DDS computes incoming_length based on sampleSize and calls memcpy() without validating incoming_data.length >= incoming_length. As a result, CacheChange_t::add_fragments() reads past the received UDP datagram buffer and into adjacent heap memory, copying those bytes into the reassembly buffer. In a Discovery Server deployment, the resulting CacheChange_t can be relayed to other participants, meaning that a newly joining participant may receive leaked heap memory (e.g., pointer values that could aid ASLR bypass). Versions 2.6.12, 2.14.6, 3.2.4, 3.3.1, and 3.4.2 fix the issue.