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 'eNB Status Transfer' message that omits the required 'MME_UE_S1AP_ID' field. This exploitation causes the MME to crash repeatedly, disrupting service.

Impact

Exploitation of this vulnerability causes a persistent crash of the Open5GS MME, disrupting all cellular communications managed by the MME, including phone calls, messaging, and data services.

Reproduction

To reproduce this vulnerability, send an 'eNB Status Transfer' message over the S1AP interface that lacks the 'MME_UE_S1AP_ID' field. This can be done by an unauthenticated mobile device or, due to the nature of the vulnerability, potentially by any entity on the Internet.

Remediation

Users can upgrade to Open5GS version 2.7.0 or later, where this vulnerability has been fixed.