CVE-2017-6129 in BIG-IP APM
Summary
by MITRE
In F5 BIG-IP APM software version 13.0.0 and 12.1.2, in some circumstances, APM tunneled VPN flows can cause a VPN/PPP connflow to be prematurely freed or cause TMM to stop responding with a "flow not in use" assertion. An attacker may be able to disrupt traffic or cause the BIG-IP system to fail over to another device in the device group.
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Analysis
by VulDB Data Team • 01/18/2023
The vulnerability identified as CVE-2017-6129 affects F5 BIG-IP APM software versions 13.0.0 and 12.1.2, representing a critical issue within the application policy manager's handling of VPN tunneling operations. This flaw manifests when specific conditions are met during APM tunneled VPN flows, creating a scenario where the system improperly manages connection flow states. The technical root cause involves a race condition or improper state management within the Traffic Management Microkernel (TMM) component that processes VPN/PPP connections. When the system encounters certain VPN tunneling scenarios, it may prematurely free connection flow resources or trigger internal assertion failures that result in system instability.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise high availability configurations within F5 BIG-IP deployments. When the TMM process becomes unresponsive due to the "flow not in use" assertion failure, the affected BIG-IP system may experience complete service interruption requiring manual intervention or automatic failover to backup devices within the device group. This behavior directly violates the expected availability guarantees that organizations rely upon from their load balancing and application delivery controllers. The vulnerability demonstrates characteristics consistent with CWE-362, a race condition flaw, where concurrent operations lead to improper resource management and system instability. The disruption can occur during normal VPN operations when legitimate users attempt to establish or maintain tunnel connections through the APM module.
From an adversarial perspective, this vulnerability presents a potential denial of service attack vector that could be exploited by malicious actors to cause service disruption or forced failovers within critical network infrastructure. The attack requires minimal privileges and can be executed through normal VPN connection establishment and maintenance activities, making it particularly dangerous in production environments where availability is paramount. The system's tendency to trigger failover mechanisms when encountering this assertion failure creates additional operational complexity for network administrators who must then investigate and resolve the underlying issue while managing potential service degradation. Organizations implementing F5 BIG-IP solutions with APM functionality should consider this vulnerability as part of their broader security posture assessment, particularly in environments where high availability and continuous service delivery are mission-critical requirements. The vulnerability aligns with ATT&CK technique T1499.004, which involves network disruption through service availability attacks, potentially enabling attackers to escalate their impact by causing system-wide failures that could compromise other network services or applications relying on the affected infrastructure.