OpenAirInterface CN5G AMF (oai-cn5g-amf) <= 2.0.0 contains a null dereference in its handling of unsupported NGAP protocol messages which allows an attacker with network-adjacent access to the AMF to carry out denial of service. When a procedure code/presence field tuple is received that is unsupported, OAI indexes into a null function pointer and subsequently dereferences it.
A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.