CVE-2025-9133 is a missing authorization vulnerability classified under CWE-862, affecting Zyxel ATP series firmware versions from V4.32 through V5.40, USG FLEX series from V4.50 through V5.40, USG FLEX 50(W) series from V4.16 through V5.40, and USG20(W)-VPN series from V4.16 through V5.40. The flaw arises because the firmware does not properly enforce authorization checks after the first stage of two-factor authentication (2FA). An attacker who has successfully completed the initial 2FA step but not the full authentication process can exploit this weakness to view and download the entire system configuration from the device. This configuration data likely contains sensitive information such as network topology, firewall rules, VPN credentials, and administrative settings. The vulnerability requires network-level access and a low privilege level (partial authentication), but no user interaction beyond that. The CVSS v3.1 base score is 8.1, reflecting high impact on confidentiality and integrity with low attack complexity and no user interaction required. No public exploits are currently known, but the vulnerability is publicly disclosed and assigned a CVE ID. The lack of patch links suggests that fixes may be forthcoming or pending deployment. This vulnerability could be leveraged by attackers to gain deep insight into network defenses and potentially facilitate further compromise or lateral movement within affected organizations.

For European organizations, the impact of CVE-2025-9133 is significant due to the potential exposure of sensitive network configuration data. Disclosure of firewall rules, VPN credentials, and administrative settings can lead to unauthorized network access, data exfiltration, and disruption of services. Organizations in sectors such as finance, healthcare, government, and critical infrastructure that rely on Zyxel ATP and USG devices for perimeter security and VPN access are particularly at risk. Attackers exploiting this vulnerability could bypass full authentication controls, undermining multi-factor authentication protections and increasing the likelihood of successful intrusions. The exposure of configuration data also facilitates targeted attacks, including privilege escalation and lateral movement. Given the widespread use of Zyxel devices in Europe, especially in small to medium enterprises and public sector entities, the vulnerability poses a broad threat. The absence of known exploits currently limits immediate risk, but the high CVSS score and ease of exploitation suggest rapid weaponization is possible once exploit code is developed.

European organizations should immediately inventory Zyxel devices to identify affected firmware versions and restrict network access to management interfaces to trusted hosts only. Deploy network segmentation and access control lists to limit exposure of vulnerable devices. Enable full two-factor authentication enforcement and monitor authentication logs for suspicious partial 2FA completions. Implement strict monitoring and alerting for configuration download attempts or unusual administrative activity. Coordinate with Zyxel for timely firmware updates and apply patches as soon as they become available. In the interim, consider disabling remote management interfaces or using VPNs with strong authentication to access device management consoles. Conduct penetration testing and vulnerability assessments focused on these devices to detect potential exploitation attempts. Finally, educate IT staff on the risks of partial authentication bypass and enforce strong credential policies.