CVE-2023-37019 in MME
Summary
by MITRE • 01/22/2025
Open5GS MME versions <= 2.6.4 contains 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 `Supported TAs` 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 CVE-2023-37019 affects Open5GS MME components version 2.6.4 and earlier, representing a critical denial of service weakness within the 5G core network infrastructure. This issue manifests through improper handling of malformed ASN.1 packets transmitted over the S1AP interface, which serves as the control plane protocol between eNodeB and MME in 4G/LTE networks. The flaw specifically targets the S1Setup Request message processing where the MME performs an assertion check that fails when the required Supported TAs field is absent from the incoming packet. This assertion failure directly translates to a remote crash condition that can be repeatedly exploited by malicious actors without requiring authentication or elevated privileges.
The technical implementation of this vulnerability stems from inadequate input validation within the Open5GS MME's S1AP message parsing logic. When an S1Setup Request message lacks the mandatory Supported TAs field as defined in the 3GPP TS 23.401 specification, the MME's assertion mechanism triggers an immediate termination of the process. This assertion failure occurs at the application level rather than being gracefully handled through proper error recovery mechanisms, leading to complete service disruption. The vulnerability aligns with CWE-617, which describes reachable assertions that can be triggered by external inputs, and represents a classic example of improper error handling in network protocol implementations. The S1AP interface operates at the control plane level and is critical for establishing and maintaining connections between network elements, making this denial of service attack particularly impactful for mobile network operators.
Operational impact of this vulnerability extends beyond simple service disruption to potentially compromising network availability and user experience across entire mobile network segments. The remote nature of the attack means that adversaries can exploit this weakness from anywhere on the network without physical access or network credentials, making it especially dangerous for public network infrastructure. The repeated triggering capability allows for sustained denial of service attacks that can persist until the MME process is manually restarted or the system is rebooted. This vulnerability directly impacts the availability component of the CIA security triad and can be categorized under ATT&CK technique T1499.004 for network denial of service attacks. Network operators may experience service degradation, dropped connections, and potential customer dissatisfaction during exploitation periods, while the attack can also serve as a precursor to more sophisticated attacks that target network infrastructure.
Mitigation strategies for CVE-2023-37019 require immediate action through software updates to versions 2.6.5 and later where the vulnerability has been patched. Network operators should implement network segmentation and access controls to limit exposure of MME components to untrusted networks, while monitoring for unusual S1AP traffic patterns that may indicate exploitation attempts. The patch addresses the root cause by implementing proper validation of the Supported TAs field before proceeding with assertion checks, ensuring that malformed packets are handled gracefully rather than causing system crashes. Organizations should also consider implementing intrusion detection systems capable of identifying malformed S1AP messages and deploying rate limiting mechanisms to prevent rapid exploitation attempts. Additionally, regular security assessments of network infrastructure components should be conducted to identify similar assertion-based vulnerabilities, and incident response procedures should be updated to address potential denial of service scenarios involving core network elements. The fix demonstrates proper secure coding practices by implementing defensive programming techniques that validate all incoming protocol messages against specification requirements before processing.