libde265 has a heap buffer overflow (OOB read) in decode_slice_unit_WPP() via out-of-bounds CtbAddrRStoTS access — libde265 <= v1.0.18

libde265 is an open source implementation of the h.265 video codec. Versions prior to 1.0.19 have a heap buffer overflow (out-of-bounds READ) exists in `decoder_context::decode_slice_unit_WPP()` in `libde265/decctx.cc`. When decoding a WPP (Wavefront Parallel Processing) HEVC slice, `ctbAddrRS` is computed as `ctbRow * ctbsWidth` inside the entry-point loop. If the PPS/SPS headers are crafted so that this value exceeds `pps.CtbAddrRStoTS.size()`, the subsequent array access `pps.CtbAddrRStoTS[ctbAddrRS]` reads past the end of the allocated vector, triggering a heap-buffer-overflow confirmed by AddressSanitizer. Version 1.0.19 patches the issue.