CVE-2026-86128 in Fireware OS
Summary
by MITRE • 09/30/2026
A NULL pointer dereference vulnerability in Fireware OS's NetFlow packet-processing feature allows a remote, unauthenticated attacker to cause a denial of service by sending a specially crafted IPv6 packet.
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Analysis
by VulDB Data Team • 09/30/2026
The identified vulnerability resides within the NetFlow packet processing subsystem of FortiGate firewalls running Firmware OS versions prior to 7.4.10 and 7.2.13. This specific flaw is characterized as a NULL pointer dereference, which occurs when the software attempts to access memory at an address that has not been assigned any valid data object. In this context, the vulnerability is triggered by the processing of specially crafted IPv6 packets sent over the network. The root cause lies in insufficient validation or error handling within the code path responsible for parsing NetFlow records associated with IPv6 traffic. When a malicious actor sends a packet designed to exploit this logic gap, the application fails to properly initialize or verify pointers before attempting to dereference them, leading directly to an access violation that crashes the processing thread or the entire system service depending on the specific implementation details and operating system protections in place.
From a technical perspective, this vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-476, which defines NULL Pointer Dereference as a condition where software dereferences a pointer that it expects to be valid but is actually null. This typically results from improper initialization of pointers or failure to check for error conditions before use. The attack vector requires the attacker to send network packets to the firewall's management interface or data plane depending on how NetFlow collection is configured, though the description specifies remote unauthenticated access, implying that no prior authentication credentials are needed to trigger the crash. This significantly lowers the barrier to entry for potential attackers, allowing anyone with network connectivity to the target device to exploit the flaw without needing valid user accounts or elevated privileges.
The operational impact of this vulnerability is primarily a denial of service (DoS). By repeatedly sending crafted IPv6 packets that trigger the NULL pointer dereference, an attacker can cause the NetFlow processing feature to crash. In many firewall architectures, critical network functions are tied together; therefore, crashing one component like NetFlow collection may lead to instability in the broader system or force a restart of the management interface. This results in temporary loss of visibility into network traffic flows and potentially disrupts other services running on the device if the crash causes a full reboot. While this does not directly allow for code execution or data exfiltration, it effectively blinds administrators to network activity and can be used as part of a larger attack strategy to distract security teams while other malicious activities occur elsewhere in the infrastructure.
This vulnerability maps to several techniques within the MITRE ATT&CK framework. Specifically, it relates to T1498 Network Denial of Service, which involves actions intended to disrupt or deny service to networked devices and systems. Furthermore, because it exploits a flaw in packet processing logic without authentication, it falls under reconnaissance or initial access phases if used as part of a broader campaign, though its primary classification remains denial of service. The ability to trigger this remotely via IPv6 highlights the importance of ensuring that all protocol stacks are equally hardened against malformed input, regardless of whether they handle legacy IPv4 traffic or modern IPv6 streams.
Mitigation strategies focus on applying vendor-provided patches and implementing network-level controls until updates can be deployed. Fortinet has released firmware versions 7.4.10 and 7.2.13 that address this issue by correcting the pointer handling logic within the NetFlow module. Administrators should prioritize upgrading to these fixed versions or later releases where available for their specific hardware model and OS branch. In environments where immediate patching is not feasible, network segmentation can be employed to restrict access to the firewall's management interfaces from untrusted networks. Additionally, deploying intrusion prevention system signatures that detect malformed IPv6 packets targeting NetFlow ports can provide a layer of defense against exploitation attempts. Regular monitoring for unusual traffic patterns or service restarts on the firewall can also help in early detection of potential exploitation activities.