An issue was discovered in libmodbus before 3.0.7 and 3.1.x before 3.1.5. There is an out-of-bounds read for the MODBUS_FC_WRITE_MULTIPLE_COILS case, aka VD-1302.
https://lists.debian.org/debian-lts-announce/2021/11/msg00020.html
https://libmodbus.org/2019/stable-and-development-releases/
https://github.com/stephane/libmodbus/commit/5ccdf5ef79d742640355d1132fa9e2abc7fbaefc