CVE-2026-103594 in Fireware OS
Summary
by MITRE • 10/27/2026
A stack-based buffer overflow vulnerability in Fireware OS's WireGuard configuration processing allows a remote attacker that has man-in-the-middle TLS-decrypted access between the Firebox and WatchGuard Cloud to create a Denial of Service condition and potentially execute arbitrary code by tampering with a FireCloud Gateway configuration payload.
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Analysis
by VulDB Data Team • 10/27/2026
The vulnerability identified in Fireware OS represents a critical security flaw within the WireGuard configuration processing subsystem, specifically affecting devices managed through the WatchGuard Cloud infrastructure. This stack-based buffer overflow occurs when the system processes configuration payloads received from the FireCloud Gateway. The root cause lies in insufficient boundary checks during the parsing of these remote configurations, allowing an attacker who has established a man-in-the-middle position to inject maliciously crafted data that exceeds the allocated memory buffers on the call stack. Because this vulnerability is triggered via network traffic decrypted by the administrator or security team for inspection, it exploits the trust placed in cloud-managed configuration updates and TLS-decrypted sessions between the endpoint device and the management console.
From a technical perspective, the exploitation of this stack-based buffer overflow allows an attacker to overwrite adjacent memory locations on the stack, potentially overwriting return addresses or function pointers. This manipulation can lead to arbitrary code execution with the privileges of the affected process, which typically runs with high-level system access. In scenarios where precise control over the overwritten data is not feasible or when the exploit triggers a crash before full shellcode execution, the vulnerability serves as an effective vector for Denial of Service attacks. These DoS conditions can disrupt network connectivity and management capabilities by crashing the WireGuard service or the entire Fireware OS instance, thereby impacting business continuity and operational availability.
The attack scenario requires specific preconditions that highlight the importance of securing not just the perimeter but also the out-of-band management channels. An attacker must possess man-in-the-middle access to the TLS-decrypted traffic between the Firebox appliance and WatchGuard Cloud. This implies that if an adversary can intercept, decrypt, or manipulate configuration updates pushed from the cloud gateway to the endpoint device, they can trigger this vulnerability. The presence of such a flaw underscores risks associated with centralized management architectures where configuration integrity is paramount. If attackers compromise the communication channel between the management console and the firewall, they gain the ability to destabilize or take control of critical network infrastructure components remotely without needing direct access to the internal network segments protected by the device.
Mitigation strategies must focus on both immediate remediation and long-term architectural hardening. The primary defense is applying the vendor-provided software updates that patch this specific buffer overflow vulnerability in WireGuard configuration processing. Organizations should ensure their Fireware OS versions are current with all security patches released following the disclosure of this issue. Additionally, securing the management channel against man-in-the-middle attacks is crucial; this includes validating TLS certificates rigorously and ensuring that only authorized entities can push configurations to managed devices. Implementing strict access controls for WatchGuard Cloud accounts and monitoring configuration change logs can help detect unauthorized attempts to manipulate device settings before they are applied.
This vulnerability aligns with Common Weakness Enumeration category CWE-121, which describes stack-based buffer overflow conditions resulting from improper boundary checks on user-controlled input. In the context of the MITRE ATT&CK framework, this flaw facilitates techniques associated with Initial Access and Execution via remote services or configuration manipulation. Specifically, it relates to components that handle network protocol parsing where memory safety is not guaranteed by default in lower-level languages like C or C++. Security teams should treat such vulnerabilities as high-priority due to their potential for both service disruption and complete system compromise, emphasizing the need for regular patch management cycles and robust monitoring of configuration change events across all managed endpoints.