CVE-2023-37017 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 `S1Setup Request` message missing a required `Global eNB ID` field to repeatedly crash the MME, resulting in denial of service.
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Analysis
by VulDB Data Team • 02/07/2025
The vulnerability identified as CVE-2023-37017 affects Open5GS MME components running versions 2.6.4 and earlier, representing a critical denial of service weakness within the 5G core network infrastructure. This flaw manifests through improper handling of malformed ASN.1 packets transmitted over the S1AP interface, which serves as the primary communication protocol between eNodeBs and the MME in 4G LTE networks that Open5GS supports. The S1AP interface operates as a critical pathway for signaling messages including initial connection establishment, mobility management, and session management procedures within the evolved packet core network architecture. When an attacker crafts and transmits a malformed S1Setup Request message lacking the required Global eNB ID field, the MME fails to properly validate the incoming packet structure, leading to an assertion failure that terminates the process.
The technical implementation of this vulnerability stems from insufficient input validation within the Open5GS MME's S1AP message parsing logic. According to CWE-248, this represents an unchecked assertion flaw where the system assumes certain conditions will always hold true without proper verification. The Global eNB ID field is mandatory in S1AP protocol specifications as it uniquely identifies the eNodeB within the network, enabling proper routing and management of signaling messages. When this field is absent or malformed, the MME's assertion mechanism triggers an immediate process termination, causing the service to crash and requiring manual intervention for restoration. The remote nature of this attack means that any network entity with access to the S1AP interface can exploit this weakness, making it particularly dangerous in production environments where network availability is paramount. The repeated triggering capability of this vulnerability allows for sustained denial of service attacks that can effectively disable critical network functions for legitimate users.
The operational impact of CVE-2023-37017 extends beyond simple service disruption, fundamentally compromising network reliability and user experience within 5G networks that depend on Open5GS implementations. Network operators utilizing affected versions face potential service outages that can affect thousands of concurrent users, particularly in scenarios where the MME handles critical mobility management functions. The vulnerability aligns with ATT&CK technique T1499.004 for network denial of service attacks, specifically targeting network infrastructure components that maintain critical signaling functions. This weakness can be exploited to create cascading failures throughout the network, as the MME's crash can disrupt ongoing connections and prevent new connections from being established. The attack vector through the S1AP interface places this vulnerability in the context of the S1AP protocol's security considerations, where proper validation of signaling messages is essential for maintaining network integrity. Additionally, the vulnerability's presence in Open5GS implementations indicates a broader concern for software quality assurance in 5G core network deployments, where proper error handling and input validation become critical security controls.
Mitigation strategies for CVE-2023-37017 primarily involve immediate software updates to versions 2.6.5 and later, which contain the necessary patches to properly validate S1AP messages and prevent assertion failures. Network administrators should implement network segmentation and access controls to limit exposure of the S1AP interface to trusted sources only, reducing the attack surface for potential exploitation. The implementation of intrusion detection systems capable of identifying malformed S1AP packets can provide early warning of attempted exploitation. Additionally, operators should conduct thorough security assessments of their Open5GS deployments to identify other potential vulnerabilities in the signaling plane and ensure proper monitoring of MME processes for unexpected terminations. According to NIST SP 800-53 security controls, implementing proper input validation and error handling mechanisms should be prioritized for mission-critical network infrastructure components. The vulnerability also highlights the importance of maintaining current security patches for 5G core network implementations and following security best practices for managing network infrastructure software lifecycle. Organizations should consider implementing redundant MME configurations and automated failover mechanisms to minimize the impact of potential service disruptions caused by similar vulnerabilities. The remediation process should include comprehensive testing of patched versions in staging environments before deployment to production networks to ensure that the fix does not introduce new compatibility issues or performance degradation.