Open5GS MME Assertion Failure Vulnerability in S1AP Interface Allowing Denial-of-Service

A denial-of-service vulnerability has been identified in Open5GS MME versions through 2.6.4. The issue arises from an assertion failure that can be remotely triggered by sending a malformed ASN.1 packet over the S1AP interface. Specifically, an attacker can exploit this vulnerability by sending an 'E-RAB Setup Response' message that omits the required 'MME_UE_S1AP_ID' field. This exploitation causes the MME to crash, leading to a persistent disruption of service.

Impact

Exploitation of this vulnerability causes the Open5GS MME to crash, disrupting all cellular communications managed by the MME, including phone calls, messaging, and data services. This disruption can persist until network operators identify and address the issue.

Reproduction

To reproduce this vulnerability, send an 'E-RAB Setup Response' S1AP packet to the Open5GS MME that is missing the 'MME_UE_S1AP_ID' field. This can be done by establishing a connection to the MME and transmitting the crafted packet over the S1AP interface.