libosdp is an implementation of IEC 60839-11-5 OSDP (Open Supervised Device Protocol) and provides a C library with support for C++, Rust and Python3. At ospd_common.c, on the osdp_reply_name function, any reply id between REPLY_ACK and REPLY_XRD is valid, but names array do not declare all of the range. On a case of an undefined reply id within the range, name will be null (name = names[reply_id - REPLY_ACK];). Null name will casue a crash on next line: if (name[0] == 0) as null[0] is invalid. As this logic is not limited to a secure connection, attacker may trigger this vulnerability without any prior knowledge. This issue is fixed in 2.4.0.
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.