CVE-2021-1272
📋 TL;DR
This vulnerability allows unauthenticated remote attackers to bypass access controls in Cisco Data Center Network Manager (DCNM) through a server-side request forgery (SSRF) attack. Attackers can send crafted HTTP requests to authenticated users to gain unauthorized access to the Device Manager application, which controls network devices. Organizations using vulnerable versions of Cisco DCNM are affected.
💻 Affected Systems
- Cisco Data Center Network Manager (DCNM)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of network devices managed by DCNM, allowing attackers to reconfigure, disrupt, or monitor critical network infrastructure.
Likely Case
Unauthorized access to network device configurations, potential data exfiltration, and lateral movement within the network.
If Mitigated
Limited impact if proper network segmentation and access controls prevent lateral movement from DCNM to managed devices.
🎯 Exploit Status
Exploitation requires sending crafted HTTP requests to authenticated users, which can be achieved through social engineering or cross-site request forgery (CSRF).
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 11.5(1) and later
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-dcnm-ssrf-F2v6q5p
Restart Required: Yes
Instructions:
1. Download DCNM version 11.5(1) or later from Cisco Software Center. 2. Backup current DCNM configuration. 3. Apply the update following Cisco DCNM upgrade procedures. 4. Restart DCNM services.
🔧 Temporary Workarounds
Restrict DCNM Web Access
linuxLimit access to DCNM web interface to trusted IP addresses only using firewall rules.
iptables -A INPUT -p tcp --dport 443 -s TRUSTED_IP_RANGE -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP
Disable Unnecessary Features
allDisable any unnecessary DCNM features or APIs that might be vulnerable, following Cisco's hardening guide.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate DCNM from critical network devices.
- Monitor DCNM logs for unusual HTTP requests and implement web application firewall (WAF) rules to block SSRF patterns.
🔍 How to Verify
Check if Vulnerable:
Check DCNM version via web interface (Admin > About) or CLI: show version | include VersionCheck Version:
show version | include VersionVerify Fix Applied:
Confirm version is 11.5(1) or later and test that crafted HTTP requests to session endpoints are properly validated.📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP requests to DCNM session validation endpoints
- Requests with unexpected parameters or URLs in session-related APIs
Network Indicators:
- HTTP traffic to DCNM with crafted parameters attempting SSRF
- Outbound requests from DCNM to internal systems not normally accessed
SIEM Query:
source="dcnm" AND (url="*session*" OR url="*validate*") AND (param="*http*" OR param="*url*")