CVE-2023-20126
📋 TL;DR
An unauthenticated remote attacker can execute arbitrary code with full privileges on Cisco SPA112 2-Port Phone Adapters by exploiting a missing authentication check in the firmware upgrade function. This affects all devices with the vulnerable web management interface exposed. No firmware update is available from Cisco to fix this vulnerability.
💻 Affected Systems
- Cisco SPA112 2-Port Phone Adapter
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attacker to install persistent backdoors, intercept all phone traffic, pivot to internal networks, or render device unusable.
Likely Case
Attacker gains full control of device to intercept VoIP calls, modify configurations, or use device as foothold for further attacks.
If Mitigated
If device is isolated from untrusted networks and firmware upgrade is disabled, risk is limited to internal threats.
🎯 Exploit Status
Exploitation requires crafting malicious firmware and triggering upgrade process. No authentication needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: None available
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-spa-unauth-upgrade-UqhyTWW
Restart Required: No
Instructions:
No official patch exists. Follow workarounds and mitigation steps below.
🔧 Temporary Workarounds
Disable Web Management Interface
allTurn off web-based management interface if not required for operations
Access device CLI via telnet/SSH
Navigate to admin settings
Disable web management interface
Network Segmentation
allIsolate SPA112 devices from untrusted networks using firewall rules
Add firewall rule: DENY all traffic to SPA112 port 80/443 from untrusted networks
Add firewall rule: DENY all traffic to SPA112 port 80/443 from internet
🧯 If You Can't Patch
- Segment devices on isolated VLAN with strict firewall rules
- Monitor for unauthorized firmware upgrade attempts and block source IPs
🔍 How to Verify
Check if Vulnerable:
Check if device model is SPA112 and web interface is accessible on port 80/443Check Version:
telnet [device_ip] 80 then GET / or check web interface login pageVerify Fix Applied:
Verify web interface is inaccessible from untrusted networks and firmware upgrade function is disabled📡 Detection & Monitoring
Log Indicators:
- Unusual firmware upgrade attempts
- Multiple failed login attempts to web interface
- Unexpected configuration changes
Network Indicators:
- HTTP POST requests to firmware upgrade endpoints from unusual sources
- Traffic spikes to device management port
SIEM Query:
source_ip=* AND dest_port=80 AND uri_path CONTAINS 'upgrade' OR 'firmware'