CVE-2023-37009 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 a `Handover Notification` 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 CVE-2023-37009 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 the S1AP interface, which serves as the control plane protocol connecting eNodeB nodes to the MME in 4G/LTE networks and the MME to the MME in 5G networks. The flaw resides in the assertion mechanism that validates incoming ASN.1 encoded packets, specifically when processing Handover Notification messages. The vulnerability stems from insufficient input validation and error handling within the MME's packet processing logic, creating a condition where malformed packets can trigger unexpected program termination.
The technical exploitation of this vulnerability occurs through the careful construction of S1AP protocol messages that contain a Handover Notification with a missing required MME_UE_S1AP_ID field. This field is essential for maintaining proper UE (User Equipment) identification and tracking within the MME's state management system. When the MME receives such a malformed packet, the assertion failure causes an immediate program crash, forcing the MME to restart and disrupting all ongoing connections within its coverage area. The vulnerability is particularly concerning because it can be repeatedly triggered without requiring authentication or specialized privileges, making it accessible to any entity capable of communicating over the S1AP interface.
The operational impact of CVE-2023-37009 extends beyond simple service disruption, as it can lead to cascading failures within the broader 5G network infrastructure. When an MME crashes repeatedly, it affects all users within its coverage area, potentially causing widespread communication outages and service degradation. The vulnerability affects the availability aspect of the network's security posture, violating the fundamental principle of service availability in the CIA triad. Network operators may experience significant operational overhead as they must monitor and restart affected MME instances, potentially leading to service level agreement violations and customer dissatisfaction.
This vulnerability aligns with CWE-617, which describes reachable assertions in software systems, and maps to ATT&CK technique T1499.004 for network denial of service attacks. The flaw demonstrates poor defensive programming practices and insufficient input sanitization, common patterns in network protocol implementations. Organizations should immediately implement mitigations including network segmentation to limit access to S1AP interfaces, deployment of intrusion detection systems to monitor for malformed S1AP traffic, and application of the vendor-provided patches. Additionally, implementing rate limiting and traffic filtering rules can help reduce the impact of repeated attack attempts while the permanent fix is being deployed.
The remediation strategy involves upgrading to Open5GS MME version 2.6.5 or later, which includes proper validation of required fields in S1AP messages and appropriate error handling for malformed packets. Network administrators should also conduct thorough vulnerability assessments of their 5G core network components and implement monitoring solutions that can detect and alert on abnormal MME behavior patterns. The vulnerability underscores the importance of robust error handling in telecommunications infrastructure and highlights the need for comprehensive security testing of protocol implementations in network control planes.