CVE-2025-1732 is a vulnerability classified under CWE-269 (Improper Privilege Management) affecting Zyxel USG FLEX H series devices running uOS firmware version 1.31 and earlier. The flaw resides in the recovery function of the firmware, where an authenticated local attacker with existing administrator privileges can upload a specially crafted configuration file. This crafted file can be used to escalate privileges beyond the current administrative level, potentially granting the attacker higher system privileges or unrestricted control over the device. The vulnerability requires local authentication with administrator rights, meaning remote unauthenticated attackers cannot exploit it directly. However, once authenticated, the attacker can manipulate the device’s configuration recovery process to bypass intended privilege restrictions. The CVSS v3.1 base score is 6.7, indicating a medium severity level, with the vector AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H. This means the attack requires local access and high privileges but has low attack complexity, no user interaction, and impacts confidentiality, integrity, and availability significantly. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability could allow attackers to gain unauthorized control, disrupt network security functions, or exfiltrate sensitive data managed by the device.

For European organizations, the impact of this vulnerability can be significant, especially for enterprises and service providers relying on Zyxel USG FLEX H series devices for network security, firewalling, and VPN services. Exploitation could lead to unauthorized privilege escalation, allowing attackers to modify security policies, disable protections, or intercept and manipulate network traffic. This could result in data breaches, service disruptions, and lateral movement within corporate networks. Given that the vulnerability requires administrator-level access, the risk is heightened in environments where credential management is weak or insider threats exist. Critical infrastructure operators, financial institutions, and government agencies using these devices could face operational disruptions and compromise of sensitive information. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits once the vulnerability becomes widely known.

1. Immediate mitigation should focus on restricting administrator access to Zyxel USG FLEX H series devices, enforcing strong multi-factor authentication (MFA) for all administrative accounts to reduce the risk of credential compromise. 2. Implement strict network segmentation to limit local access to the management interfaces of these devices, ensuring only trusted personnel and systems can connect. 3. Regularly audit and monitor administrative activities and configuration changes on the devices to detect suspicious behavior indicative of exploitation attempts. 4. Since no official patches are currently available, consider deploying compensating controls such as disabling the recovery function if feasible or restricting the upload of configuration files to trusted sources only. 5. Maintain an up-to-date asset inventory to identify all Zyxel USG FLEX H series devices and prioritize remediation efforts accordingly. 6. Engage with Zyxel support channels to obtain information on forthcoming patches or firmware updates and plan timely deployment once available. 7. Educate administrators on the risks of privilege escalation vulnerabilities and enforce the principle of least privilege to minimize potential damage.