CVE-2016-9247 in BIG-IP
Summary
by MITRE
Under certain conditions for BIG-IP systems using a virtual server with an associated FastL4 profile and TCP analytics profile, a specific sequence of packets may cause the Traffic Management Microkernel (TMM) to restart.
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Analysis
by VulDB Data Team • 04/20/2025
The vulnerability identified as CVE-2016-9247 represents a critical stability issue within F5 BIG-IP systems that can lead to denial of service conditions through unexpected restarts of the Traffic Management Microkernel. This flaw specifically impacts systems configured with virtual servers utilizing both FastL4 profiles and TCP analytics profiles, creating a dangerous combination that can be exploited through carefully crafted packet sequences. The vulnerability operates at the core networking layer where packet processing and session management intersect, making it particularly concerning for enterprise environments that rely heavily on consistent network service availability.
The technical mechanism behind this vulnerability involves a specific sequence of TCP packets that triggers a condition within the TMM process where memory management or state tracking mechanisms fail to handle the packet flow properly. When these particular packets are processed in the context of a FastL4 profile combined with TCP analytics, the system enters an unpredictable state that ultimately results in the TMM restarting. This restart effectively disrupts all active connections and services managed by that particular TMM instance, leading to immediate service degradation or complete unavailability of the affected virtual servers. The vulnerability demonstrates a classic case of improper input validation and state handling within network processing components, which aligns with CWE-248, representing an unchecked exception in the system's packet processing pipeline.
The operational impact of CVE-2016-9247 extends beyond simple service disruption to encompass broader security and operational concerns for organizations using F5 BIG-IP solutions. Network administrators face the challenge of maintaining service availability while the vulnerability exists, as the restart condition can be triggered by legitimate traffic patterns or malicious actors seeking to disrupt services. The timing and conditions required for exploitation mean that this vulnerability could potentially be weaponized in targeted attacks against critical infrastructure, particularly in environments where network availability is paramount. Organizations may experience cascading effects from these restarts, as multiple virtual servers or services could be affected simultaneously, leading to extended outages and increased operational complexity during incident response.
Mitigation strategies for CVE-2016-9247 should focus on immediate patching of affected F5 BIG-IP systems through official vendor updates, as well as implementing network-level controls to monitor and filter potentially malicious packet sequences. Security teams should also consider temporary configuration changes that remove or modify the problematic FastL4 and TCP analytics profile combinations until permanent fixes are applied. The vulnerability's characteristics suggest it may be exploitable through techniques aligned with ATT&CK tactic TA0043 (Reconnaissance) and TA0045 (Security Testing) where adversaries might attempt to identify and exploit system weaknesses. Organizations should also implement monitoring solutions that can detect unusual restart patterns or TMM behavior that could indicate exploitation attempts, as well as establish incident response procedures specifically addressing this type of denial of service condition. Additionally, network segmentation and access controls should be reviewed to limit the potential impact of successful exploitation attempts.