CVE-2020-3309
📋 TL;DR
This vulnerability in Cisco Firepower Device Manager (FDM) On-Box software allows authenticated remote attackers to overwrite arbitrary files on the underlying operating system. Attackers can exploit this by uploading malicious files due to improper input validation. Organizations using affected Cisco Firepower devices with FDM On-Box are at risk.
💻 Affected Systems
- Cisco Firepower Threat Defense (FTD)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to modify operating system files, install persistent backdoors, disable security controls, or render the device inoperable.
Likely Case
Attackers overwrite configuration files to bypass security policies, gain elevated privileges, or maintain persistence on the device.
If Mitigated
Limited impact with proper network segmentation, strong authentication controls, and monitoring preventing successful exploitation.
🎯 Exploit Status
Exploitation requires valid administrative credentials to the FDM interface. No public exploit code was available at advisory publication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Cisco FTD software release 6.6.1 and later
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fdmfo-HvPWKxDe
Restart Required: Yes
Instructions:
1. Download Cisco FTD software version 6.6.1 or later from Cisco Software Center. 2. Upload the software image to the FDM interface. 3. Install the update through the FDM upgrade wizard. 4. Reboot the device when prompted to complete the installation.
🔧 Temporary Workarounds
Restrict FDM access
allLimit access to the FDM management interface to trusted IP addresses only
Configure ACLs on management interfaces to restrict access to specific source IPs
Use FMC management
allMigrate from FDM On-Box management to Firepower Management Center (FMC)
Export configuration from FDM, reimage device for FMC management, import configuration to FMC
🧯 If You Can't Patch
- Implement strict network segmentation to isolate FDM management interfaces
- Enforce strong authentication policies including multi-factor authentication for administrative accounts
🔍 How to Verify
Check if Vulnerable:
Log into FDM web interface, navigate to System > Updates, check current software version. If version is below 6.6.1, device is vulnerable.Check Version:
show version (from CLI) or check System > Updates in FDM web interfaceVerify Fix Applied:
After patching, verify software version shows 6.6.1 or higher in System > Updates. Test file upload functionality to ensure proper validation.📡 Detection & Monitoring
Log Indicators:
- Unusual file upload activities in FDM logs
- Multiple failed authentication attempts followed by successful login
- Configuration changes from unexpected sources
Network Indicators:
- Unusual traffic patterns to/from FDM management interface
- File upload requests to FDM API endpoints
SIEM Query:
source="ftd_logs" AND (event_type="file_upload" OR action="upload") AND result="success"