CVE-2018-15322 in BIG-IP
Summary
by MITRE
On BIG-IP 14.0.0-14.0.0.2, 13.0.0-13.1.0.7, 12.1.0-12.1.3.5, 11.6.0-11.6.3.2, or 11.2.1-11.5.6, BIG-IQ Centralized Management 6.0.0-6.0.1, 5.0.0-5.4.0 or 4.6.0, BIG-IQ Cloud and Orchestration 1.0.0, iWorkflow 2.0.1-2.3.0, or Enterprise Manager 3.1.1 a BIG-IP user granted with tmsh access may cause the BIG-IP system to experience denial-of-service (DoS) when the BIG-IP user uses the tmsh utility to run the edit cli preference command and proceeds to save the changes to another filename repeatedly. This action utilises storage space on the /var partition and when performed repeatedly causes the /var partition to be full.
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Analysis
by VulDB Data Team • 06/04/2023
This vulnerability exists within F5 BIG-IP systems across multiple version ranges including 14.0.0-14.0.0.2, 13.0.0-13.1.0.7, 12.1.0-12.1.3.5, 11.6.0-11.6.3.2, and 11.2.1-11.5.6, as well as BIG-IQ Centralized Management 6.0.0-6.0.1, 5.0.0-5.4.0, 4.6.0, BIG-IQ Cloud and Orchestration 1.0.0, iWorkflow 2.0.1-2.3.0, and Enterprise Manager 3.1.1. The flaw manifests when a BIG-IP user with tmsh access executes the edit cli preference command and subsequently saves changes to a different filename repeatedly. This behavior represents a classic denial-of-service condition that exploits insufficient input validation and resource management within the system's configuration handling mechanisms. The vulnerability specifically targets the /var partition storage space, which serves as a critical system area for temporary files, logs, and runtime data.
The technical exploitation occurs through the tmsh utility's handling of cli preference modifications where repeated save operations create persistent file entries without proper cleanup or size limitations. Each execution of the save command with a new filename consumes additional space on the /var partition, which has finite storage capacity. The vulnerability stems from the lack of proper resource accounting and file management controls within the tmsh command processing logic. When this process is repeated multiple times, it rapidly consumes available storage space, eventually leading to a complete partition exhaustion. This storage exhaustion prevents the system from performing normal operations, effectively causing a denial-of-service condition that can render the BIG-IP appliance non-functional. The vulnerability is categorized as a resource exhaustion issue under CWE-400, specifically manifesting as a storage exhaustion condition that affects system availability.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire network infrastructure dependencies. BIG-IP appliances serve as critical components for load balancing, application delivery, and network security, making this DoS condition particularly dangerous in production environments. When the /var partition becomes full, the system cannot write necessary log files, temporary data, or configuration updates, which can cascade into complete system failure. Network administrators may experience complete loss of access to the appliance, requiring manual intervention to recover from the storage exhaustion state. The vulnerability also represents a potential attack vector for persistent DoS campaigns where malicious actors could repeatedly trigger the condition to maintain system unavailability. This issue aligns with ATT&CK technique T1499.004 for network denial-of-service attacks and demonstrates how seemingly benign administrative commands can be weaponized for system compromise.
Mitigation strategies should focus on both immediate remediation and long-term defensive measures. Organizations must apply the vendor-provided security patches and updates that address the specific tmsh command handling behavior. System administrators should implement monitoring solutions to track /var partition usage and establish automated alerts when storage thresholds approach critical levels. The tmsh utility access should be restricted to authorized personnel only, with proper access controls enforced through role-based permissions. Additionally, implementing configuration management policies that prevent repeated save operations to the same configuration context can help reduce the attack surface. Network segmentation and firewall rules should be configured to limit access to tmsh interfaces from trusted networks only. Regular system audits should verify that no unauthorized users possess tmsh access privileges, and system logs should be monitored for suspicious repeated save operations. The vulnerability highlights the importance of proper input validation and resource management within privileged system utilities, emphasizing the need for comprehensive security testing of administrative interfaces and the implementation of robust resource accounting mechanisms.