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.