CVE-2024-21771 in BIG-IP AFM
Summary
by MITRE • 02/14/2024
For unspecified traffic patterns, BIG-IP AFM IPS engine may spend an excessive amount of time matching the traffic against signatures, resulting in Traffic Management Microkernel (TMM) restarting and traffic disruption. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated
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Analysis
by VulDB Data Team • 01/24/2025
The vulnerability identified as CVE-2024-21771 affects the BIG-IP Advanced Firewall Manager (AFM) IPS engine within F5 Networks' BIG-IP platform. This issue represents a significant operational concern for organizations relying on F5's traffic management solutions, as it directly impacts the availability and performance of network security services. The vulnerability specifically manifests when the IPS engine processes certain traffic patterns that cause excessive matching time against security signatures, leading to system instability and service disruption.
The technical flaw resides in the Traffic Management Microkernel (TMM) component of the BIG-IP system, which is responsible for processing network traffic and applying security policies. When the IPS engine encounters specific traffic patterns, it enters a state where signature matching operations consume disproportionate system resources and processing time. This condition ultimately triggers an automatic restart of the TMM process, causing temporary loss of network connectivity and service interruption for affected traffic flows. The vulnerability is categorized under CWE-778, which addresses insufficient logging or monitoring of security-relevant events, though the primary issue stems from resource exhaustion during signature matching operations.
From an operational perspective, this vulnerability poses substantial risk to enterprise network infrastructure as it can lead to cascading failures in security services. Organizations utilizing BIG-IP AFM for intrusion prevention may experience unexpected service outages, particularly during high-traffic periods or when processing specific malicious traffic patterns. The restart of TMM processes creates a window of service disruption that can impact business continuity and network availability. Security teams may also face challenges in identifying the root cause of service interruptions, as the system behavior appears as an unexpected restart rather than a more explicit resource exhaustion condition.
The impact extends beyond simple service disruption to encompass broader security implications for network infrastructure. Organizations may experience increased operational overhead as security teams must respond to unexpected system restarts and investigate potential security incidents. The vulnerability also affects compliance requirements for network availability and security monitoring, as the system's behavior may not align with expected operational characteristics. Network administrators should consider implementing monitoring solutions that can detect TMM restart patterns and correlate them with security events to maintain visibility into system health and potential security threats.
Mitigation strategies should focus on both immediate remediation and long-term monitoring approaches. Organizations should prioritize applying the latest F5 security patches and updates that address this specific vulnerability, as recommended by F5's security advisories and the National Cybersecurity Database. Network security teams should implement enhanced monitoring for TMM restart events and establish alerting mechanisms to detect anomalous behavior patterns that may indicate exploitation attempts. Additionally, organizations should consider implementing traffic filtering rules that can prevent or reduce exposure to the specific traffic patterns that trigger this vulnerability. The ATT&CK framework's T1499 sub-technique for Network Denial of Service should be considered when developing incident response procedures, as this vulnerability could potentially be leveraged to create service disruption attacks against affected systems.