CVE-2023-37005 in MME
Summary
by MITRE • 01/22/2025
Open5GS MME versions <= 2.6.4 contain an assertion that can be remotely triggered via a malformed ASN.1 packet over the S1AP interface. An attacker may send an `Initial Context Setup Failure` message missing a required `MME_UE_S1AP_ID` field to repeatedly crash the MME, resulting in denial of service.
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Analysis
by VulDB Data Team • 01/22/2025
The vulnerability identified as CVE-2023-37005 affects Open5GS MME components running versions 2.6.4 and earlier, representing a critical security flaw within the mobile network infrastructure that supports 4G LTE operations. This issue manifests through the S1AP protocol interface, which serves as the control plane interface between the Evolved NodeB (eNB) and the MME in LTE networks. The flaw stems from inadequate input validation mechanisms within the MME's handling of ASN.1 encoded packets, specifically when processing Initial Context Setup Failure messages that are part of the S1AP signaling procedures. The vulnerability is classified under CWE-248, which addresses the exposure of an exception to an attacker, and aligns with ATT&CK technique T1499.004 for network denial of service attacks.
The technical implementation of this vulnerability exploits the absence of proper validation for mandatory fields within the ASN.1 packet structure. When an attacker sends a malformed Initial Context Setup Failure message through the S1AP interface, the packet lacks the required MME_UE_S1AP_ID field that the MME expects during normal operation. This missing field triggers an assertion failure within the Open5GS MME codebase, causing the process to terminate unexpectedly. The assertion mechanism, designed to catch programming errors during development, becomes a vector for denial of service when manipulated by external actors. The vulnerability is particularly concerning because it allows for repeated triggering of the assertion failure, enabling sustained denial of service attacks that can disrupt mobile network services for legitimate users.
The operational impact of this vulnerability extends beyond simple service disruption, as it affects the core functionality of mobile network infrastructure that supports critical communications services. When the MME crashes repeatedly due to this vulnerability, it causes cascading failures throughout the LTE network, potentially affecting thousands of concurrent users within the affected network segment. The service disruption can last until manual intervention occurs to restart the MME service or until the system automatically recovers from the crash, which may not occur immediately. Network operators relying on Open5GS for their 4G core network infrastructure face significant risk of service degradation or complete network outages, particularly in environments where mobile connectivity is essential for emergency services, industrial operations, or enterprise communications.
Mitigation strategies for this vulnerability primarily focus on immediate patching of affected Open5GS MME components to versions 2.6.5 or later, where the assertion failure has been addressed through proper input validation. Network administrators should implement network monitoring solutions that can detect anomalous S1AP traffic patterns and alert operators to potential exploitation attempts. The implementation of rate limiting and packet filtering mechanisms at the S1AP interface can help reduce the impact of repeated attack attempts. Additionally, organizations should consider deploying intrusion detection systems specifically configured to monitor for malformed S1AP messages and establish incident response procedures that include immediate MME service restart capabilities. This vulnerability demonstrates the importance of robust input validation in telecommunication protocols and highlights the need for comprehensive security testing of network infrastructure components before deployment in production environments.