CVE-2026-71933 in VigorSwitch G2540xs
Summary
by MITRE • 08/24/2026
Multiple DrayTek VigorSwitch models contain unauthorized operation vulnerabilities in multiple syslog functions. The vulnerability is caused by missing authorization checks. A remote attacker can trigger these vulnerabilities via crafted requests to modify configuration, restart services, save startup configuration, or clear logs.
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Analysis
by VulDB Data Team • 08/24/2026
The identified security flaw resides within the Syslog management subsystem of various DrayTek VigorSwitch network devices, representing a critical failure in access control mechanisms. This vulnerability stems from missing authorization checks on multiple syslog-related functions that are exposed to remote attackers via standard network protocols. In secure system design, administrative actions such as modifying device configurations or managing logging services must be strictly gated behind robust authentication and privilege verification processes. The absence of these controls allows unauthenticated users to interact with sensitive operational endpoints directly over the network without providing valid credentials. This architectural deficiency effectively bypasses the intended security boundary, granting external actors the ability to execute privileged commands that should only be accessible to authorized administrators.
The technical impact of this vulnerability is severe due to the breadth of actions an attacker can perform once they exploit these unauthenticated entry points. By sending crafted requests to the affected syslog functions, a remote adversary can modify critical device configurations, which may alter routing tables, firewall rules, or VLAN assignments, thereby compromising network integrity and availability. Furthermore, the ability to restart services remotely can lead to denial of service conditions by disrupting essential networking daemons required for switch operation. The capability to save startup configuration changes allows an attacker to persist their modifications across reboots, ensuring that malicious settings remain active even after device maintenance cycles. Additionally, the function to clear logs enables attackers to erase evidence of their intrusion and subsequent activities, significantly hindering forensic analysis and incident response efforts by security teams attempting to trace the attack vector or assess the scope of compromise.
From a classification perspective, this vulnerability aligns with CWE-284, which describes Improper Access Control, specifically highlighting the failure to enforce proper authorization checks before allowing access to sensitive resources. The exploitation technique maps closely to MITRE ATT&CK techniques related to Defense Evasion and Persistence, as clearing logs serves to obscure activity while modifying configurations ensures long-term control over the device. This scenario exemplifies a common class of vulnerabilities found in Internet of Things (IoT) and network infrastructure hardware where convenience or legacy code practices have led to overly permissive default states for administrative interfaces. The lack of input validation combined with insufficient authentication creates an environment ripe for automated exploitation tools that scan for such misconfigurations across large segments of the internet.
To mitigate this risk, immediate action is required to address both the specific vulnerability and broader security hygiene practices on affected devices. DrayTek has likely released firmware updates that patch these missing authorization checks; therefore, administrators should verify their current software version against vendor advisories and apply all available patches promptly. In environments where updating is not immediately feasible, network segmentation strategies can help isolate vulnerable switches from untrusted networks, restricting access to management interfaces only through trusted IP ranges using firewall rules or VLAN isolation. Additionally, enabling strong authentication mechanisms for all administrative ports and disabling unused services reduces the attack surface. Regular auditing of device configurations and log integrity checks are also recommended to detect any unauthorized changes that may have occurred prior to remediation. Continuous monitoring for anomalous traffic patterns targeting management interfaces can provide early warning indicators of exploitation attempts in real-time.