CVE-2020-3297
📋 TL;DR
CVE-2020-3297 allows unauthenticated remote attackers to bypass authentication on Cisco Small Business Smart and Managed Switches by brute-forcing weak session IDs. This enables session hijacking with administrative privileges. Organizations using affected Cisco switches with web management interfaces exposed are vulnerable.
💻 Affected Systems
- Cisco Small Business Smart Switches
- Cisco Small Business Managed Switches
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of network switch with administrative access, enabling network traffic interception, configuration changes, and potential lateral movement to other systems.
Likely Case
Unauthorized access to switch management interface leading to configuration changes, network disruption, or credential harvesting.
If Mitigated
Limited impact if switches are patched, management interfaces are isolated, and network segmentation is implemented.
🎯 Exploit Status
Exploitation requires brute-forcing session IDs which is straightforward with available tools. No authentication required.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Varies by model - refer to Cisco advisory for specific firmware versions
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sbswitch-session-JZAS5jnY
Restart Required: Yes
Instructions:
1. Identify affected switch models and current firmware. 2. Download appropriate firmware from Cisco support site. 3. Backup current configuration. 4. Upload and install new firmware via web interface or CLI. 5. Verify installation and restore configuration if needed.
🔧 Temporary Workarounds
Disable web management interface
allDisable HTTP/HTTPS management access and use CLI or other management methods
no ip http server
no ip http secure-server
Restrict management access
allLimit management interface access to trusted IP addresses only
ip http access-class <ACL-NAME>
ip http secure-server access-class <ACL-NAME>
🧯 If You Can't Patch
- Isolate management interfaces to dedicated VLAN with strict access controls
- Implement network segmentation to limit potential lateral movement from compromised switches
🔍 How to Verify
Check if Vulnerable:
Check switch firmware version against Cisco advisory. Use 'show version' command and compare to affected versions list.Check Version:
show versionVerify Fix Applied:
Verify firmware version after update matches patched versions in Cisco advisory. Test session ID generation for improved entropy.📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts followed by successful login from same IP
- Session ID brute force patterns in web logs
- Configuration changes from unexpected sources
Network Indicators:
- Unusual HTTP/HTTPS traffic to switch management interfaces
- Multiple session ID requests in short timeframes
SIEM Query:
source="switch_logs" ("authentication failed" count>10 within 1m) OR ("session" AND "brute")