CVE-2013-4656
📋 TL;DR
This CVE describes a symlink traversal vulnerability in ASUS RT-AC66U and RT-N56U routers due to SMB service misconfiguration. Attackers can exploit this to access arbitrary files on the router's filesystem. This affects users of these specific ASUS router models with default configurations.
💻 Affected Systems
- ASUS RT-AC66U
- ASUS RT-N56U
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete router compromise allowing remote code execution, credential theft, network traffic interception, and persistent backdoor installation.
Likely Case
Unauthorized file access leading to configuration file theft, credential harvesting, and potential privilege escalation.
If Mitigated
Limited impact with proper network segmentation and access controls preventing external exploitation.
🎯 Exploit Status
Exploitation is straightforward using symlink traversal techniques against the SMB service.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware versions after 2013 (specific version numbers vary by model)
Vendor Advisory: https://www.asus.com/support/
Restart Required: Yes
Instructions:
1. Log into router admin interface. 2. Navigate to Firmware Upgrade section. 3. Download latest firmware from ASUS support site. 4. Upload and apply firmware update. 5. Reboot router.
🔧 Temporary Workarounds
Disable SMB Service
allTurn off the vulnerable SMB service completely
Login to router admin panel -> USB Application -> Network Place (Samba) Share -> Disable
Restrict SMB Access
allLimit SMB service to trusted internal networks only
Login to router admin panel -> Firewall -> Access Control -> Restrict SMB ports
🧯 If You Can't Patch
- Replace affected routers with newer models or different vendors
- Implement strict network segmentation to isolate routers from critical assets
🔍 How to Verify
Check if Vulnerable:
Check router firmware version and compare against patched versions from ASUS advisory. Test SMB service for symlink traversal using security tools.Check Version:
Login to router admin interface and check System Status or Firmware Version pageVerify Fix Applied:
Verify firmware version is updated to patched version. Test SMB service to confirm symlink traversal no longer works.📡 Detection & Monitoring
Log Indicators:
- Unusual SMB access patterns
- Multiple failed SMB authentication attempts
- Access to sensitive system files via SMB
Network Indicators:
- SMB traffic to router from external sources
- Unusual port 445/tcp activity to router
SIEM Query:
source_ip=external AND dest_ip=router_ip AND dest_port=445 AND protocol=SMB🔗 References
- https://www.ise.io/casestudies/exploiting-soho-routers/
- https://www.ise.io/soho_service_hacks/
- https://www.ise.io/wp-content/uploads/2017/07/soho_techreport.pdf
- https://www.ise.io/casestudies/exploiting-soho-routers/
- https://www.ise.io/soho_service_hacks/
- https://www.ise.io/wp-content/uploads/2017/07/soho_techreport.pdf
