CVE-2021-1277
📋 TL;DR
This vulnerability in Cisco Data Center Network Manager allows attackers to spoof trusted hosts or perform man-in-the-middle attacks due to insufficient HTTPS certificate validation. Attackers could intercept, modify, or steal sensitive API communications. Organizations using affected DCNM versions are at risk.
💻 Affected Systems
- Cisco Data Center Network Manager
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of DCNM management system, allowing attacker to intercept all API communications, modify network configurations, steal credentials and sensitive data, and potentially pivot to other network systems.
Likely Case
Interception of sensitive API communications, extraction of credentials and configuration data, unauthorized modification of network settings, and potential privilege escalation within the DCNM environment.
If Mitigated
Limited impact with proper network segmentation, certificate pinning, and monitoring; attacker may still intercept some communications but with reduced access to critical systems.
🎯 Exploit Status
Exploitation requires network access to intercept HTTPS traffic between DCNM and other systems. The vulnerability is in certificate validation logic, making man-in-the-middle attacks feasible.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 11.5(1) and later
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-dcnm-cert-check-BdZZV9T3
Restart Required: Yes
Instructions:
1. Download DCNM version 11.5(1) or later from Cisco Software Center. 2. Backup current configuration. 3. Install the update following Cisco's upgrade guide. 4. Restart DCNM services. 5. Verify certificate validation is working properly.
🔧 Temporary Workarounds
Implement Certificate Pinning
allConfigure DCNM to only accept specific certificates from trusted hosts
# Configure in DCNM web interface under Security > Certificate Management
# Use CLI: configure certificate-pinning enable
Network Segmentation
allIsolate DCNM management traffic from untrusted networks
# Configure firewall rules to restrict DCNM API traffic
# Example: iptables -A INPUT -s trusted_hosts -p tcp --dport 443 -j ACCEPT
🧯 If You Can't Patch
- Implement strict network segmentation to isolate DCNM from untrusted networks
- Enable comprehensive logging and monitoring of all DCNM API communications
- Use VPN tunnels for all DCNM communications with external systems
- Implement certificate pinning and strict certificate validation policies
🔍 How to Verify
Check if Vulnerable:
Check DCNM version via web interface (Help > About) or CLI command: show version. If version is earlier than 11.5(1), system is vulnerable.Check Version:
show versionVerify Fix Applied:
After patching, verify version is 11.5(1) or later. Test certificate validation by attempting to connect with invalid certificates - connections should be rejected.📡 Detection & Monitoring
Log Indicators:
- Failed SSL/TLS handshakes
- Certificate validation errors
- Unexpected API request sources
- Multiple failed authentication attempts
Network Indicators:
- Unusual traffic patterns to DCNM API endpoints
- SSL/TLS interception attempts
- Traffic from unexpected IP addresses to DCNM
SIEM Query:
source="dcnm" AND (event_type="ssl_error" OR event_type="certificate_error" OR event_type="authentication_failure")