Open5GS MME versions <= 2.6.4 contain a buffer overflow in the ASN.1 deserialization function of the S1AP handler. This buffer overflow causes type confusion in decoded fields, leading to invalid parsing and freeing of memory. An attacker may use this to crash an MME or potentially execute code in certain circumstances.
The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.
While assertion is good for catching logic errors and reducing the chances of reaching more serious vulnerability conditions, it can still lead to a denial of service. For example, if a server handles multiple simultaneous connections, and an assert() occurs in one single connection that causes all other connections to be dropped, this is a reachable assertion that leads to a denial of service.