An issue was discovered in FRRouting FRR through 9.0. bgp_nlri_parse_flowspec in bgpd/bgp_flowspec.c processes malformed requests with no attributes, leading to a NULL pointer dereference.
https://lists.debian.org/debian-lts-announce/2023/09/msg00020.html
https://github.com/FRRouting/frr/pull/13222/commits/cfd04dcb3e689754a72507d086ba3b9709fc5ed8