CVE-2021-42758
📋 TL;DR
This vulnerability allows authenticated low-privilege users on FortiWLC wireless LAN controllers to bypass GUI restrictions and execute arbitrary commands with full administrative privileges. It affects FortiWLC versions 8.6.1 and below. Attackers can gain complete control of affected systems through improper access control mechanisms.
💻 Affected Systems
- Fortinet FortiWLC
📦 What is this software?
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
Fortiwlc by Fortinet
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the wireless controller allowing attacker to reconfigure network settings, intercept traffic, deploy malware to connected devices, and use the system as a pivot point to attack internal networks.
Likely Case
Attacker gains administrative access to modify wireless network configurations, create rogue access points, intercept sensitive data, and potentially compromise connected client devices.
If Mitigated
Limited impact if proper network segmentation, least privilege access, and monitoring are in place to detect and contain unauthorized administrative actions.
🎯 Exploit Status
Exploitation requires authenticated access but is straightforward once an attacker has valid low-privilege credentials. The vulnerability bypasses GUI restrictions rather than requiring complex technical exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: FortiWLC 8.6.2 and later
Vendor Advisory: https://fortiguard.com/advisory/FG-IR-21-200
Restart Required: Yes
Instructions:
1. Download FortiWLC 8.6.2 or later from Fortinet support portal. 2. Backup current configuration. 3. Upload and install the new firmware via web interface or CLI. 4. Reboot the controller. 5. Verify the update was successful and restore configuration if needed.
🔧 Temporary Workarounds
Restrict low-privilege user access
allRemove or disable all low-privilege user accounts until patching can be completed
config system admin
edit [username]
set accprofile "prof_admin"
end
Network segmentation and access control
allRestrict management interface access to trusted IP addresses only
config system interface
edit [management-interface]
set allowaccess https ssh
set trustedhost [trusted-ip-range]
end
🧯 If You Can't Patch
- Implement strict network segmentation to isolate FortiWLC management interfaces from untrusted networks
- Enable detailed logging and monitoring for all administrative actions and implement alerting for privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check FortiWLC firmware version via web interface (System > Status) or CLI command 'get system status'Check Version:
get system status | grep VersionVerify Fix Applied:
Verify firmware version is 8.6.2 or later and test that low-privilege users cannot execute administrative commands📡 Detection & Monitoring
Log Indicators:
- Unusual administrative commands executed by low-privilege users
- Multiple failed privilege escalation attempts followed by successful administrative actions
- Configuration changes from non-admin user accounts
Network Indicators:
- Unusual administrative API calls from low-privilege user sessions
- Multiple authentication attempts followed by administrative command execution
SIEM Query:
source="fortiwlc" AND (event_type="admin_action" AND user_role="low_privilege") OR (event_type="config_change" AND user_role!="admin")