CVE-2019-6590 in BIG-IP LTM
Summary
by MITRE
On BIG-IP LTM 13.0.0 to 13.0.1 and 12.1.0 to 12.1.3.6, under certain conditions, the TMM may consume excessive resources when processing SSL Session ID Persistence traffic.
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Analysis
by VulDB Data Team • 07/06/2023
The vulnerability identified as CVE-2019-6590 affects F5 BIG-IP Local Traffic Manager (LTM) appliances running specific versions of the software stack. This issue represents a resource exhaustion flaw that impacts the Traffic Management Microkernel (TMM) component responsible for processing network traffic. The vulnerability exists within the SSL Session ID Persistence functionality, which is a critical feature for maintaining session state across multiple SSL connections in load balancing scenarios. The affected versions include BIG-IP LTM 13.0.0 through 13.0.1 and 12.1.0 through 12.1.3.6, indicating this is a long-term issue affecting multiple release branches. From a cybersecurity perspective, this vulnerability aligns with CWE-400 which categorizes resource exhaustion vulnerabilities as a significant threat to system availability and performance. The vulnerability demonstrates characteristics consistent with the ATT&CK technique T1499.004 which involves resource exhaustion attacks targeting availability through malicious use of system resources.
The technical flaw manifests when the TMM component processes SSL Session ID Persistence traffic under specific conditions that trigger excessive resource consumption. This occurs during the handling of SSL session identifiers that are used to maintain session state across multiple connections, a common practice in load balancing and application delivery scenarios. The vulnerability does not require authentication or specific user interaction to be exploited, making it particularly dangerous as it can be triggered by normal network traffic patterns. The resource consumption typically affects memory and CPU utilization within the TMM process, potentially leading to system instability or complete service disruption. The conditions under which this occurs are not explicitly detailed in the CVE description but likely involve specific patterns of session ID reuse or malformed session data that causes the TMM to enter an inefficient processing loop.
The operational impact of CVE-2019-6590 extends beyond simple performance degradation to potentially causing complete service outages for organizations relying on F5 BIG-IP appliances for their application delivery needs. When the TMM consumes excessive resources, it can lead to system crashes, unresponsiveness, or the inability to process new incoming connections. This vulnerability particularly affects organizations with high SSL traffic volumes where session persistence is heavily utilized, as the resource exhaustion can cascade through the entire load balancing infrastructure. The impact is especially severe in environments where F5 appliances serve as critical components in application delivery, web application firewalls, or SSL termination points. Organizations may experience extended downtime, service degradation, or require manual intervention to restore normal operations, making this a critical availability threat that affects business continuity.
Organizations should immediately implement mitigations including applying the latest security patches from F5 as recommended in their security advisory. The patch addresses the root cause by improving the handling of SSL Session ID Persistence traffic to prevent excessive resource consumption. Network administrators should also consider implementing traffic monitoring and alerting mechanisms to detect unusual resource consumption patterns that may indicate exploitation attempts. Additional mitigations include temporarily disabling SSL Session ID Persistence functionality if not critical to operations, implementing rate limiting on SSL connections, and monitoring system resources closely for signs of resource exhaustion. Organizations should also review their security posture and ensure proper network segmentation to limit the potential impact of exploitation. The vulnerability demonstrates the importance of maintaining up-to-date security patches and implementing comprehensive monitoring strategies to detect and respond to resource exhaustion attacks. Given the nature of the vulnerability, organizations should also consider implementing intrusion detection systems that can identify abnormal traffic patterns associated with this specific exploit.