CVE-2023-37014 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 a `UE Context Release Request` 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 • 01/23/2025
The vulnerability identified as CVE-2023-37014 affects Open5GS MME components running versions 2.6.4 and earlier, representing a critical denial of service weakness within the mobile network infrastructure. This flaw manifests through improper handling of malformed ASN.1 packets transmitted over the S1AP interface, which serves as the primary communication channel between the Evolved NodeB and the MME in 4G LTE networks. The S1AP protocol operates at the application layer and manages signaling procedures including initial attach, paging, and context release operations that are fundamental to maintaining user equipment connectivity within the cellular network.
The technical implementation of this vulnerability stems from an insufficient input validation mechanism within the MME's handling of UE Context Release Request messages. Specifically, the system contains an assertion that fails when processing a `UE Context Release Request` message lacking the required `MME_UE_S1AP_ID` field, which is essential for identifying the specific user equipment context being released. This assertion failure occurs during the packet parsing phase of the S1AP interface processing, where the MME's software logic does not adequately validate the presence of mandatory fields before proceeding with subsequent operations. The absence of proper error handling for malformed packets creates a condition where repeated exploitation can cause the MME process to terminate unexpectedly, leading to complete service disruption for all connected user equipment within the affected network segment.
The operational impact of this vulnerability extends beyond simple service interruption as it can be exploited remotely without requiring authentication or specialized privileges, making it particularly dangerous in production network environments. An attacker positioned to send packets to the S1AP interface can repeatedly send malformed `UE Context Release Request` messages, causing the MME to crash repeatedly and forcing a complete restart of the service. This vulnerability directly violates the principle of fault tolerance that is fundamental to telecommunications infrastructure, as it allows an attacker to cause sustained disruption to network operations. The repeated crashing behavior creates a cascading effect where network stability is compromised, potentially affecting thousands of connected users simultaneously and creating service degradation that impacts not only individual user experiences but also the overall network reliability and availability.
The weakness aligns with CWE-248, which describes an unchecked exception in software systems, and represents a classic example of improper input validation in network protocol implementations. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers network disruption attacks, and T1566.002, covering spearphishing via social media, as attackers could potentially exploit this vulnerability through network-based attacks. Mitigation strategies should include immediate patching to versions 2.6.5 and later where the assertion handling has been corrected, implementing network segmentation to limit access to the S1AP interface, and deploying intrusion detection systems capable of identifying malformed S1AP packets. Additionally, network administrators should establish monitoring procedures to detect unusual MME crash patterns and implement rate limiting on S1AP message processing to prevent rapid exploitation attempts. The vulnerability highlights the importance of robust input validation and proper exception handling in telecommunications software, particularly in systems handling real-time user equipment signaling where reliability is paramount to maintaining network service availability.