CVE-2024-20450
📋 TL;DR
This critical vulnerability allows unauthenticated remote attackers to execute arbitrary commands with root privileges on Cisco SPA300/500 series IP phones. Attackers can exploit it by sending specially crafted HTTP requests to the web management interface, leading to buffer overflow. Organizations using these affected phone models are at risk.
💻 Affected Systems
- Cisco Small Business SPA300 Series IP Phones
- Cisco Small Business SPA500 Series IP Phones
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of affected IP phones allowing attackers to install persistent malware, intercept calls, pivot to internal networks, or render devices unusable.
Likely Case
Attackers gain full control of vulnerable phones to eavesdrop on communications, steal credentials, or use as foothold for lateral movement.
If Mitigated
Limited impact if phones are isolated from internet and internal network segmentation prevents lateral movement.
🎯 Exploit Status
No authentication required, simple HTTP request exploitation makes this highly attractive to attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Cisco advisory for specific firmware versions
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-spa-http-vulns-RJZmX2Xz
Restart Required: Yes
Instructions:
1. Download latest firmware from Cisco support portal. 2. Upload firmware to phone via web interface. 3. Reboot phone after installation. 4. Verify firmware version post-update.
🔧 Temporary Workarounds
Disable web management interface
allDisable HTTP/HTTPS management access if not required for operations
Access phone web interface > Admin > Advanced > Disable Web Server
Network segmentation
allIsolate IP phones on separate VLAN with strict firewall rules
🧯 If You Can't Patch
- Immediately isolate affected phones from internet and restrict internal network access
- Implement strict network monitoring for HTTP traffic to phone management interfaces
🔍 How to Verify
Check if Vulnerable:
Check firmware version via phone web interface or physical display menuCheck Version:
Access phone web interface > Admin > Status > Firmware VersionVerify Fix Applied:
Confirm firmware version matches patched version from Cisco advisory📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP requests to phone management interface
- Multiple failed login attempts followed by successful access
- Unexpected firmware version changes
Network Indicators:
- HTTP POST requests with abnormal payload sizes to phone management ports
- Traffic from unexpected sources to phone management interface
SIEM Query:
source_ip=* AND dest_port=(80,443,8080) AND http_user_agent CONTAINS 'malicious' AND device_type='cisco_phone'