CVE-2024-9677
📋 TL;DR
This vulnerability allows an authenticated local attacker to steal an administrator's authentication token from the CLI command in USG FLEX H series firewalls, enabling privilege escalation. The attack requires the administrator to be currently logged in and not have logged out. Only users with local access to the firewall are affected.
💻 Affected Systems
- Zyxel USG FLEX H series firewalls
📦 What is this software?
Uos by Zyxel
⚠️ Risk & Real-World Impact
Worst Case
An authenticated local attacker gains full administrative privileges, potentially compromising the entire firewall configuration, network security policies, and gaining access to sensitive network traffic.
Likely Case
A malicious insider or compromised user account escalates privileges to administrator level, allowing unauthorized configuration changes and access to sensitive firewall data.
If Mitigated
With proper access controls and monitoring, the impact is limited to potential configuration changes that can be detected and rolled back.
🎯 Exploit Status
Exploitation requires the attacker to have authenticated local access to the firewall CLI and for an administrator to be currently logged in.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: uOS firmware version V1.22 or later
Restart Required: Yes
Instructions:
1. Download the latest firmware from Zyxel support portal. 2. Backup current configuration. 3. Upload and install firmware version V1.22 or later. 4. Reboot the firewall. 5. Verify the firmware version after reboot.
🔧 Temporary Workarounds
Enforce strict session management
allImplement policies requiring administrators to log out immediately after completing tasks and enforce session timeouts.
Restrict CLI access
allLimit CLI access to only necessary administrative personnel and implement strong authentication controls.
🧯 If You Can't Patch
- Implement strict access controls to limit who has local authenticated access to the firewall CLI
- Monitor administrator login sessions and enforce immediate logout policies after administrative tasks are completed
🔍 How to Verify
Check if Vulnerable:
Check the firmware version via the web interface (System > Maintenance > Firmware) or CLI command 'show version' and verify if it is V1.21 or earlier.Check Version:
show versionVerify Fix Applied:
After patching, verify the firmware version shows V1.22 or later using the same methods.📡 Detection & Monitoring
Log Indicators:
- Unusual privilege escalation attempts in system logs
- Multiple administrator login sessions from the same user
- Unauthorized configuration changes
Network Indicators:
- Unexpected firewall rule changes
- Unusual administrative traffic patterns
SIEM Query:
source="firewall_logs" AND (event_type="privilege_escalation" OR event_type="unauthorized_config_change")