CVE-2025-1732 in USG FLEX H uOS
Summary
by MITRE • 04/22/2025
An improper privilege management vulnerability in the recovery function of the Zyxel USG FLEX H series uOS firmware version V1.31 and earlier could allow an authenticated local attacker with administrator privileges to upload a crafted configuration file and escalate privileges on a vulnerable device.
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Analysis
by VulDB Data Team • 10/31/2025
The vulnerability identified as CVE-2025-1732 represents a critical improper privilege management flaw within the recovery function of Zyxel USG FLEX H series devices running uOS firmware version V1.31 and earlier. This issue specifically targets the device's configuration recovery mechanism, which is designed to restore system functionality during maintenance or failure scenarios. The vulnerability arises from insufficient validation of uploaded configuration files during the recovery process, creating an exploitable path for authenticated local attackers who already possess administrator credentials.
The technical exploitation of this vulnerability hinges on the device's failure to properly validate the integrity and permissions of configuration files during the recovery procedure. When an authenticated administrator uploads a crafted configuration file through the recovery function, the system processes the file without adequate checks for privilege escalation vectors. This weakness allows the attacker to inject malicious configuration elements that can modify system permissions or execute elevated operations within the device's operational context. The flaw essentially undermines the principle of least privilege by permitting administrative operations that should be restricted to the system's core privileged processes.
From an operational impact perspective, this vulnerability presents a significant risk to network infrastructure security as it allows for privilege escalation within a device that is already compromised by an authenticated attacker. The affected Zyxel USG FLEX H series devices are commonly deployed in enterprise environments where they serve as critical network security appliances managing firewall policies, routing decisions, and access controls. Successful exploitation could enable attackers to gain unauthorized access to network traffic monitoring capabilities, modify firewall rules to bypass security controls, or establish persistent access points within the network infrastructure. The recovery function typically operates with elevated privileges to ensure system restoration, making it a prime target for privilege escalation attacks.
The vulnerability aligns with CWE-276, which addresses improper privilege management, and demonstrates characteristics consistent with ATT&CK technique T1068, which involves the use of privilege escalation to gain elevated access. Organizations deploying these devices face heightened risk of insider threats or compromised administrator accounts, as the vulnerability does not require additional authentication beyond existing administrative access. The attack surface is limited to local network access with existing administrative credentials, but this constraint does not diminish the severity of potential impacts. The recovery function's design flaw creates a persistent backdoor opportunity that remains active until firmware is updated, potentially allowing attackers to maintain access across device reboots or recovery operations.
Mitigation strategies should prioritize immediate firmware updates to versions that address the privilege management deficiency in the recovery function. Network administrators should implement strict access controls and monitor for unauthorized configuration file uploads through the recovery interface. Additional protective measures include restricting physical and network access to administrative interfaces, implementing multi-factor authentication for administrative accounts, and conducting regular security audits of device configurations. The vulnerability also highlights the importance of secure configuration management practices and the need for comprehensive testing of recovery mechanisms to prevent similar privilege escalation paths in network security appliances.