CVE-2023-37023 in MME
Summary
by MITRE • 01/22/2025
Open5GS MME versions <= 2.6.4 contain a reachable assertion in the `Uplink NAS Transport` packet handler. A packet missing its `MME_UE_S1AP_ID` field causes Open5gs to crash; an attacker may repeatedly send such packets to cause denial of service.
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Analysis
by VulDB Data Team • 02/07/2025
The vulnerability identified as CVE-2023-37023 affects Open5GS MME components version 2.6.4 and earlier, representing a critical flaw in the mobile network infrastructure software that governs 4G LTE core network operations. This issue manifests within the `Uplink NAS Transport` packet handler, which processes incoming signaling messages from user equipment to the network's mobility management entity. The flaw stems from inadequate input validation mechanisms that fail to properly handle malformed packets lacking essential identification fields required for proper message processing. The specific absence of the `MME_UE_S1AP_ID` field in these packets triggers an assertion failure within the software's execution flow, causing the MME process to terminate abruptly and resulting in complete service disruption for connected user equipment.
This vulnerability operates at the protocol level within the LTE core network architecture, specifically impacting the S1AP (S1 Application Protocol) interface that connects the eNodeB (base station) to the MME. The technical implementation flaw resides in the packet parsing logic where the software assumes the presence of mandatory fields without proper verification before proceeding with subsequent processing steps. When a malformed packet arrives without the required `MME_UE_S1AP_ID` field, the assertion mechanism triggers a program termination rather than gracefully handling the error condition through proper error recovery procedures. This design choice violates fundamental principles of robust software engineering and fault tolerance, creating a single point of failure that can be easily exploited by malicious actors. The vulnerability aligns with CWE-617, which addresses reachable assertions, and demonstrates poor error handling practices that can lead to system instability.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader network reliability concerns within 4G LTE deployments. An attacker capable of sending malicious packets to the MME can repeatedly exploit this flaw to cause repeated service outages, effectively performing a denial of service attack against the mobile network infrastructure. The MME serves as a critical component in the LTE core network, managing mobility, authentication, and session control functions for all connected user equipment. When compromised through this vulnerability, the entire network's ability to maintain service for subscribers becomes compromised, potentially affecting thousands of concurrent users depending on the network's scale and configuration. The attack vector requires minimal sophistication as it only necessitates sending malformed packets to the target MME, making it particularly dangerous for network operators who may not have adequate monitoring or rate limiting in place to detect such attacks.
Mitigation strategies for CVE-2023-37023 should prioritize immediate software updates to versions 2.6.5 and later, which contain the necessary patches to address the assertion failure. Network operators should implement comprehensive monitoring solutions to detect unusual packet patterns and establish rate limiting mechanisms to prevent abuse of this vulnerability. The implementation of proper input validation and error handling procedures should be enforced throughout the software stack, with defensive programming practices such as using try-catch blocks and graceful degradation mechanisms. Organizations should also consider deploying intrusion detection systems that can identify and alert on malformed S1AP packets, particularly those lacking required identification fields. Additionally, implementing network segmentation and access controls to limit direct exposure of MME components to untrusted networks can reduce the attack surface. The vulnerability's classification under ATT&CK technique T1499.004 highlights the importance of maintaining robust network resilience and implementing proper incident response procedures to address such infrastructure-level attacks that can severely impact mobile network availability and service quality.