CVE-2021-26093
📋 TL;DR
This vulnerability allows a local authenticated attacker to crash managed access points by executing a crafted CLI command on FortiWLC controllers. The issue stems from an uninitialized pointer access that can cause denial of service. Affected users include organizations running vulnerable FortiWLC versions for wireless network management.
💻 Affected Systems
- FortiWLC
📦 What is this software?
Fortiwlc by Fortinet
⚠️ Risk & Real-World Impact
Worst Case
Complete denial of service for wireless access points managed by the controller, disrupting network connectivity for all wireless clients.
Likely Case
Temporary service disruption of specific access points requiring manual intervention to restore functionality.
If Mitigated
Limited impact with proper access controls preventing unauthorized CLI access and monitoring for suspicious commands.
🎯 Exploit Status
Exploitation requires authenticated CLI access and knowledge of the specific crafted command. No public exploit code has been disclosed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 8.6.1 and 8.5.4
Vendor Advisory: https://fortiguard.com/psirt/FG-IR-21-002
Restart Required: Yes
Instructions:
1. Download the patched firmware version from Fortinet support portal. 2. Backup current configuration. 3. Upload and install the new firmware through the web interface or CLI. 4. Reboot the controller to apply changes.
🔧 Temporary Workarounds
Restrict CLI Access
allLimit CLI access to authorized administrators only using role-based access controls.
configure system admin
edit <username>
set accprofile "super_admin"
end
Monitor CLI Commands
allEnable logging and monitoring of CLI commands for suspicious activity.
config log syslogd setting
set status enable
set server "<syslog_server_ip>"
end
🧯 If You Can't Patch
- Implement strict access controls to limit CLI access to essential personnel only
- Monitor for unusual CLI command patterns and access point crash events
🔍 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 8.6.1 or 8.5.4 or later after patching📡 Detection & Monitoring
Log Indicators:
- Access point disconnection events
- Unusual CLI command execution patterns
- System crash/reboot logs
Network Indicators:
- Sudden loss of connectivity to managed access points
- Increased authentication failures for wireless clients
SIEM Query:
source="fortiwlc" AND (event_type="ap_disconnect" OR event_type="cli_command") | stats count by user, command