CVE-2019-6661 in BIG-IP APM
Summary
by MITRE
When the BIG-IP APM 14.1.0-14.1.2, 14.0.0-14.0.1, 13.1.0-13.1.3.1, 12.1.0-12.1.4.1, or 11.5.1-11.6.5 system processes certain requests, the APD/APMD daemon may consume excessive resources.
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Analysis
by VulDB Data Team • 02/23/2024
The vulnerability identified as CVE-2019-6661 affects F5 BIG-IP Access Policy Manager (APM) systems across multiple version ranges including 14.1.0-14.1.2, 14.0.0-14.0.1, 13.1.0-13.1.3.1, 12.1.0-12.1.4.1, and 11.5.1-11.6.5. This issue manifests when the APD/APMD daemon processes specific types of requests, leading to excessive resource consumption that can ultimately result in system degradation or denial of service. The affected daemon operates within the BIG-IP APM framework which is designed to manage access policies and authentication for network resources, making this vulnerability particularly concerning for organizations relying on F5 appliances for their security infrastructure. The resource consumption occurs during the processing of certain requests that trigger abnormal behavior in the daemon's memory management or processing loops, creating a potential attack vector for resource exhaustion attacks.
The technical flaw resides in the improper handling of specific request patterns by the APD/APMD daemon component of the BIG-IP system. When these particular requests are processed, the daemon enters into a state where it consumes increasingly large amounts of system resources such as memory and cpu cycles without proper resource limiting or cleanup mechanisms. This behavior represents a classic resource exhaustion vulnerability where malicious actors can repeatedly send crafted requests to cause the daemon to consume all available resources, leading to system instability, application crashes, or complete service unavailability. The vulnerability is categorized under CWE-400 as "Uncontrolled Resource Consumption" and aligns with ATT&CK technique T1499.1 for "Endpoint Denial of Service" as it specifically targets the resource management capabilities of the system to achieve denial of service conditions.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire security infrastructure of organizations relying on F5 BIG-IP appliances. When the APD/APMD daemon consumes excessive resources, it affects not only the access policy management functions but can also impact other critical system processes that depend on the same resource pools. Organizations may experience complete loss of access control capabilities, inability to authenticate users, and potential compromise of network security policies that rely on the APM system. The vulnerability particularly affects enterprise environments where access policies are heavily utilized for managing user access to applications and network resources, making it a significant concern for cybersecurity teams responsible for maintaining secure network access controls.
Mitigation strategies for CVE-2019-6661 should prioritize immediate patching of affected systems with the vendor-provided security updates. Organizations should implement monitoring solutions to detect unusual resource consumption patterns in their BIG-IP systems, particularly focusing on memory and cpu utilization of the APD/APMD daemon processes. Network segmentation and access controls should be implemented to limit the exposure of vulnerable systems to potentially malicious traffic, while also establishing baseline performance metrics to quickly identify when resource consumption exceeds normal operational parameters. Additionally, organizations should review their access policy configurations to minimize the attack surface and implement rate limiting mechanisms to prevent abuse of the vulnerable request processing paths. The remediation process should include comprehensive testing of patched systems to ensure that the vulnerability has been fully addressed without introducing compatibility issues with existing access policies and authentication mechanisms.