CVE-2020-3382
📋 TL;DR
This vulnerability allows unauthenticated remote attackers to bypass authentication in Cisco Data Center Network Manager (DCNM) REST API and execute arbitrary actions with administrative privileges. It affects DCNM installations that share a static encryption key, enabling attackers to craft valid session tokens. All organizations running vulnerable DCNM versions are affected.
💻 Affected Systems
- Cisco Data Center Network Manager (DCNM)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of DCNM infrastructure, allowing attackers to reconfigure network devices, exfiltrate sensitive data, deploy ransomware, or disrupt data center operations.
Likely Case
Unauthorized administrative access leading to network configuration changes, credential theft, lateral movement to connected systems, and data exfiltration.
If Mitigated
Limited impact if proper network segmentation, access controls, and monitoring are in place to detect and block exploitation attempts.
🎯 Exploit Status
Exploitation is straightforward once the static key is obtained. Public proof-of-concept code exists, making this easily weaponizable.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 11.4(1) and later
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-dcnm-bypass-dyEejUMs
Restart Required: Yes
Instructions:
1. Download DCNM version 11.4(1) or later from Cisco Software Center. 2. Backup current configuration. 3. Apply the update following Cisco's upgrade guide. 4. Restart DCNM services. 5. Verify the update was successful.
🔧 Temporary Workarounds
Network Access Restriction
linuxRestrict access to DCNM REST API to trusted IP addresses only
iptables -A INPUT -p tcp --dport 443 -s TRUSTED_IP -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP
API Endpoint Disablement
linuxDisable the vulnerable REST API endpoints if not required
# Modify DCNM configuration to disable REST API or restrict to localhost
🧯 If You Can't Patch
- Isolate DCNM systems in a separate network segment with strict firewall rules
- Implement network-based intrusion detection to monitor for authentication bypass attempts
🔍 How to Verify
Check if Vulnerable:
Check DCNM version via web interface or SSH: show version | include VersionCheck Version:
show version | include VersionVerify Fix Applied:
Verify version is 11.4(1) or later and attempt to reproduce exploit using known POC (in test environment only)📡 Detection & Monitoring
Log Indicators:
- Failed authentication attempts followed by successful admin API calls
- Unusual API requests from unexpected IP addresses
- Session token generation without proper authentication
Network Indicators:
- Unusual REST API traffic patterns
- Administrative API calls from unauthenticated sources
- Traffic to /rest/ endpoints from external IPs
SIEM Query:
source="dcnm.logs" AND ("authentication bypass" OR "invalid token" OR "admin API" from external_ip)