CVE-2018-15318 in BIG-IP
Summary
by MITRE
In BIG-IP 14.0.0-14.0.0.2, 13.1.0.4-13.1.1.1, or 12.1.3.4-12.1.3.6, if an MPTCP connection receives a HUDCTL_ABORT while the initial flow is not the primary flow, the initial flow will remain after the MP_FASTCLOSE procedure is complete. TMM may restart and produce a core file as a result of this condition.
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Analysis
by VulDB Data Team • 06/04/2023
This vulnerability affects F5 BIG-IP systems running specific versions of the Traffic Management Microkernel (TMM) and represents a critical memory management flaw that can lead to system instability and potential denial of service conditions. The issue manifests when Multi-Path TCP (MPTCP) connections encounter a HUDCTL_ABORT control message under specific flow conditions, creating a scenario where the initial flow fails to properly terminate during the MP_FASTCLOSE procedure. This improper flow handling creates a memory state inconsistency that can trigger TMM restarts and generate core dump files, indicating severe system instability. The vulnerability impacts multiple major versions including 14.0.0 through 14.0.0.2, 13.1.0.4 through 13.1.1.1, and 12.1.3.4 through 12.1.3.6, suggesting a widespread issue affecting the fundamental connection handling mechanisms within the BIG-IP platform. According to CWE classification, this represents a weakness in the system's resource management and memory handling capabilities, specifically related to improper cleanup of connection states during abnormal termination scenarios.
The technical exploitation of this vulnerability occurs through the manipulation of MPTCP connection state transitions, specifically when the HUDCTL_ABORT message is processed in non-primary flow contexts. During normal MPTCP operation, when a connection experiences issues, the system should properly close all associated flows through the MP_FASTCLOSE procedure. However, in this flaw, the system fails to properly terminate the initial flow when it is not designated as the primary flow, leaving stale connection states in memory. This condition creates a memory leak scenario where connection resources are not properly released, and the system's state machine becomes inconsistent. The TMM process, which handles all traffic processing on BIG-IP systems, becomes unstable when encountering this state inconsistency, leading to automatic restarts and core file generation. The underlying mechanism involves the interaction between MPTCP's flow management and the BIG-IP's connection tracking systems, where the abort processing logic does not properly account for the flow hierarchy and state dependencies.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the availability and reliability of critical network infrastructure. When TMM restarts occur due to this condition, it results in temporary loss of network connectivity for services handled by the affected BIG-IP system, creating a denial of service scenario that can affect thousands of concurrent connections depending on the system configuration. The core file generation indicates that the system has encountered a critical error state that requires manual intervention for analysis and recovery. Organizations relying on BIG-IP systems for load balancing, application delivery, and network security may experience significant operational disruption, particularly in high-availability environments where such restarts can trigger failover processes and service degradation. This vulnerability particularly affects environments using MPTCP for enhanced connection reliability, making it a significant concern for organizations implementing advanced networking protocols on their BIG-IP appliances.
Mitigation strategies for this vulnerability should focus on immediate patch application and monitoring of system stability indicators. F5 released security patches addressing this specific issue in their subsequent software releases, and organizations should prioritize upgrading to patched versions of the BIG-IP software. Network administrators should implement monitoring solutions to detect TMM restart patterns and core file generation that may indicate this vulnerability's exploitation. The ATT&CK framework categorizes this as a system compromise technique through resource exhaustion and process manipulation, where attackers could potentially trigger the condition to cause service disruption. Additional defensive measures include implementing connection tracking monitoring to detect anomalous MPTCP behavior and configuring system alerting for TMM restart events. Organizations should also consider implementing network segmentation to limit the impact scope and establish recovery procedures for rapid system restoration following any TMM restart incidents. The vulnerability's classification under CWE 459 indicates that proper resource cleanup and state management procedures are insufficiently implemented, requiring comprehensive code review and testing of connection termination logic in affected systems.