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 'Initial UE Message' that omits the required 'PLMN Identity' field. This exploitation causes the MME to crash repeatedly, 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 'Initial UE Message' over the S1AP interface that lacks the 'PLMN Identity' field. This can be done by an unauthenticated mobile device or, due to the availability of Wi-Fi Calling services, by any entity on the Internet.