CVE-2016-1473
📋 TL;DR
Cisco Small Business 220 switches with vulnerable firmware have a hardcoded SNMP community string that cannot be changed. This allows remote attackers to read or modify SNMP objects without authentication, potentially compromising network devices. All users of affected Cisco 220 series switches with firmware before 1.0.1.1 are vulnerable.
💻 Affected Systems
- Cisco Small Business 220 Series Smart Switches
📦 What is this software?
Small Business 220 Series Smart Plus Switches by Cisco
View all CVEs affecting Small Business 220 Series Smart Plus Switches →
⚠️ Risk & Real-World Impact
Worst Case
Complete network compromise through SNMP write access allowing configuration changes, traffic redirection, device takeover, and network disruption.
Likely Case
Network reconnaissance, configuration data theft, and potential unauthorized configuration changes leading to service disruption.
If Mitigated
Limited to SNMP read-only access if write community is disabled, still exposing sensitive network information.
🎯 Exploit Status
Exploitation requires only knowledge of the hardcoded community string, which is publicly documented. Simple SNMP tools can be used.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware 1.0.1.1 or later
Vendor Advisory: http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160831-sps3
Restart Required: Yes
Instructions:
1. Download firmware 1.0.1.1 or later from Cisco support site. 2. Backup current configuration. 3. Upload new firmware via web interface or CLI. 4. Reboot switch to apply update. 5. Verify firmware version after reboot.
🔧 Temporary Workarounds
Disable SNMP or restrict access
allDisable SNMP service entirely or restrict SNMP access using ACLs
configure terminal
no snmp-server community public
no snmp-server enable
snmp-server community private RO 10
access-list 10 permit 192.168.1.0 0.0.0.255
access-list 10 deny any
🧯 If You Can't Patch
- Isolate affected switches in separate VLAN with strict network segmentation
- Implement network monitoring for SNMP traffic to/from affected devices
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface or CLI command 'show version'. If version is below 1.0.1.1, device is vulnerable.Check Version:
show version | include VersionVerify Fix Applied:
After patching, verify firmware version is 1.0.1.1 or higher and test SNMP access with default community strings should fail.📡 Detection & Monitoring
Log Indicators:
- SNMP authentication failures
- Unexpected SNMP configuration changes
- Multiple SNMP requests from single source
Network Indicators:
- SNMP traffic to/from affected devices using default community strings
- SNMP write requests from unauthorized sources
SIEM Query:
source_port=161 AND (community_string="public" OR community_string="private") AND dest_ip=[switch_ip]🔗 References
- http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160831-sps3
- http://www.securityfocus.com/bid/92710
- http://www.securitytracker.com/id/1036711
- http://www.synacktiv.com/ressources/advisories_cisco_switch_sg220_default_snmp.pdf
- http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160831-sps3
- http://www.securityfocus.com/bid/92710
- http://www.securitytracker.com/id/1036711
- http://www.synacktiv.com/ressources/advisories_cisco_switch_sg220_default_snmp.pdf
