CVE-2026-86104 in Fireware OS
Summary
by MITRE • 09/30/2026
An uncontrolled resource consumption vulnerability in the Fireware OS login process (wgagent) allows a remote, unauthenticated attacker to cause a denial of service by sending a specially crafted request.
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Analysis
by VulDB Data Team • 09/30/2026
The identified vulnerability resides within the wgagent component of WatchGuard Firebox Operating System, specifically affecting the authentication and login handling mechanisms. This flaw is classified as an uncontrolled resource consumption issue, which fundamentally stems from insufficient validation or rate-limiting controls when processing incoming connection requests during the initial handshake phase. The technical nature of this defect allows a remote attacker who has not yet authenticated to interact with the service in a manner that triggers disproportionate resource allocation relative to the computational effort required by the client. By sending specially crafted network packets, an adversary can exploit this logic error to force the wgagent process into repetitive or excessive internal operations, such as memory allocation loops or CPU-intensive cryptographic computations without corresponding progress toward successful authentication. This behavior effectively drains system resources, leading to a state where legitimate administrative traffic cannot be processed due to resource exhaustion.
From a security architecture perspective, this vulnerability aligns with CWE-400, which describes uncontrolled resource consumption within the Common Weakness Enumeration framework. The attack vector is remote and requires no prior authentication credentials, placing it in the highest risk category for availability impacts. In terms of tactical classification under the MITRE ATT&CK framework, this activity corresponds to techniques associated with Denial of Service (DoS) attacks, specifically those that target service availability through resource exhaustion rather than direct system crash or privilege escalation. The attacker leverages the open nature of the management interface to send malformed or excessively large requests that trigger internal processing loops within the wgagent daemon. Because this component is critical for managing firewall policies and user access, its degradation directly compromises the operational integrity of the entire security perimeter device.
The operational impact of exploiting this vulnerability is severe, primarily manifesting as a denial of service condition where administrators lose connectivity to the Firebox management interface. This loss of control prevents authorized personnel from applying security updates, modifying firewall rules, or monitoring network traffic in real-time. In high-availability environments or critical infrastructure deployments, such an outage can lead to significant business disruption and potential exposure to other threats if failover mechanisms are not properly configured or also affected by the resource strain. Furthermore, because the vulnerability exists before authentication is established, it serves as a potent tool for attackers seeking to disrupt services without needing to bypass complex password policies or exploit additional credential-based weaknesses.
Mitigation strategies must focus on both immediate remediation and long-term architectural hardening. The primary defense involves applying vendor-provided software patches that address the logic errors within the wgagent component, ensuring that input validation is strictly enforced and resource limits are appropriately capped for unauthenticated sessions. Network-level controls should be implemented to restrict access to the management interface exclusively from trusted IP addresses using firewalls or VLAN segmentation, thereby reducing the attack surface available to remote adversaries. Additionally, implementing rate-limiting policies on administrative ports can help mitigate the effectiveness of such exhaustion attacks by throttling excessive connection attempts before they consume critical system resources. Regular monitoring for unusual spikes in CPU and memory usage associated with management services should also be established to detect potential exploitation attempts early.