CVE-2025-1731
📋 TL;DR
An incorrect permission assignment vulnerability in PostgreSQL commands in Zyxel USG FLEX H series firewalls allows authenticated local attackers with low privileges to gain Linux shell access and escalate privileges. Attackers can craft malicious scripts or modify system configurations with administrator-level access using stolen tokens. This affects Zyxel USG FLEX H series firewalls running uOS firmware versions V1.20 through V1.31.
💻 Affected Systems
- Zyxel USG FLEX H series firewalls
📦 What is this software?
Uos by Zyxel
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise where attacker gains root access, modifies firewall rules, intercepts network traffic, installs persistent backdoors, and accesses sensitive data.
Likely Case
Privilege escalation to administrator level, allowing configuration changes, network rule modifications, and potential lateral movement within the network.
If Mitigated
Limited impact if proper access controls, network segmentation, and monitoring are in place to detect unusual privilege escalation attempts.
🎯 Exploit Status
Exploitation requires authenticated access and knowledge of PostgreSQL command injection techniques. Token theft adds additional complexity.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: V1.32 or later
Restart Required: Yes
Instructions:
1. Download firmware V1.32 or later from Zyxel support portal. 2. Backup current configuration. 3. Upload and install new firmware via web interface. 4. Reboot device. 5. Verify firmware version.
🔧 Temporary Workarounds
Restrict Local Access
allLimit local shell access to trusted administrators only and implement strict access controls.
Session Management
allEnforce administrator logout policies and implement session timeout to invalidate tokens.
🧯 If You Can't Patch
- Implement network segmentation to isolate affected firewalls from critical systems.
- Enable detailed logging and monitoring for privilege escalation attempts and unusual PostgreSQL activity.
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface: System > Maintenance > Firmware. If version is between V1.20 and V1.31 inclusive, device is vulnerable.Check Version:
Not applicable - use web interface for version checkVerify Fix Applied:
After patching, verify firmware version shows V1.32 or later in System > Maintenance > Firmware.📡 Detection & Monitoring
Log Indicators:
- Unusual PostgreSQL command execution
- Privilege escalation attempts
- Multiple failed authentication attempts followed by successful low-privilege access
- Session token anomalies
Network Indicators:
- Unexpected configuration changes to firewall rules
- Unusual outbound connections from firewall management interface
SIEM Query:
source="zyxel_firewall" AND (event_type="privilege_escalation" OR command="postgresql" AND user!="admin")