CVE-2025-1731 in USG FLEX H uOS
Summary
by MITRE • 04/22/2025
An incorrect permission assignment vulnerability in the PostgreSQL commands of the Zyxel USG FLEX H series uOS firmware versions from V1.20 through V1.31 could allow an authenticated local attacker with low privileges to gain access to the Linux shell and escalate their privileges by crafting malicious scripts or modifying system configurations with administrator-level access through a stolen token. Modifying the system configuration is only possible if the administrator has not logged out and the token remains valid.
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Analysis
by VulDB Data Team • 10/31/2025
The vulnerability identified as CVE-2025-1731 represents a critical permission assignment flaw within the Zyxel USG FLEX H series uOS firmware versions ranging from V1.20 through V1.31. This issue specifically affects the PostgreSQL command execution mechanisms and creates a pathway for authenticated local attackers to escalate their privileges and gain unauthorized access to the underlying Linux shell environment. The vulnerability stems from improper access control implementations that fail to adequately validate user permissions before executing sensitive system commands, creating a significant security gap in the device's authorization framework.
The technical exploitation of this vulnerability requires an authenticated local user with low privileges to craft malicious scripts or manipulate system configurations that would normally require administrator-level access. The attack vector leverages a stolen token mechanism where the attacker can utilize a valid administrative token to perform privileged operations without proper authentication checks. This flaw directly maps to CWE-284 which describes improper access control vulnerabilities, and specifically aligns with ATT&CK technique T1068 which covers privilege escalation through legitimate user credentials. The vulnerability's exploitation process involves bypassing the normal permission validation mechanisms that should prevent low-privilege users from executing administrative commands.
The operational impact of this vulnerability is severe as it allows attackers to achieve full system compromise through a relatively simple attack chain that does not require external network access or complex exploitation techniques. Once an attacker successfully exploits this vulnerability, they can execute arbitrary commands with root privileges, modify system configurations, access sensitive data, and potentially establish persistent backdoors within the network infrastructure. The attack requires only local access and an existing valid administrative token, making it particularly dangerous in environments where administrative credentials might be compromised through other means. This vulnerability effectively undermines the principle of least privilege and creates a persistent threat vector for attackers who gain access to any local user account.
Mitigation strategies for CVE-2025-1731 should focus on immediate firmware updates to versions that address the permission assignment flaw, along with implementing strict access control policies that enforce token expiration and regular credential rotation. Network administrators should disable unnecessary local access where possible and implement monitoring for suspicious administrative command execution patterns. The vulnerability highlights the importance of proper input validation and access control implementation in network security devices, emphasizing that even low-privilege users should not be able to execute administrative functions without proper authorization checks. Organizations should also consider implementing additional security controls such as mandatory access controls, privilege separation mechanisms, and regular security audits to prevent similar issues from occurring in other network infrastructure components. The vulnerability serves as a reminder of the critical need for comprehensive security testing of network device firmware and the importance of maintaining up-to-date security patches to protect against known vulnerabilities.