CVE-2021-20034
📋 TL;DR
CVE-2021-20034 is an improper access control vulnerability in SonicWall SMA100 appliances that allows unauthenticated attackers to bypass path traversal checks and delete arbitrary files. This could lead to a reboot to factory default settings, potentially causing service disruption and configuration loss. Organizations using affected SonicWall SMA100 versions are vulnerable.
💻 Affected Systems
- SonicWall Secure Mobile Access (SMA) 100 series
📦 What is this software?
Sma 500v by Sonicwall
Sma 500v by Sonicwall
Sma 500v by Sonicwall
⚠️ Risk & Real-World Impact
Worst Case
Complete system reset to factory defaults, causing extended service downtime, loss of all configurations, and potential credential exposure requiring full device reconfiguration.
Likely Case
Service disruption through file deletion leading to system instability or reboot, potentially requiring manual intervention to restore functionality.
If Mitigated
Minimal impact with proper network segmentation and access controls preventing external exploitation attempts.
🎯 Exploit Status
Public exploit code available on Packet Storm Security demonstrates password reset capability through file deletion.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 10.2.1.0-18sv and later
Vendor Advisory: https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0021
Restart Required: Yes
Instructions:
1. Download latest firmware from SonicWall support portal. 2. Backup current configuration. 3. Apply firmware update via web interface or CLI. 4. Reboot device. 5. Verify version is 10.2.1.0-18sv or later.
🔧 Temporary Workarounds
Network Segmentation
allRestrict access to SMA100 management interface to trusted internal networks only
Access Control Lists
allImplement firewall rules to block external access to SMA100 web interface
🧯 If You Can't Patch
- Isolate SMA100 appliance behind firewall with strict inbound rules
- Implement network monitoring for suspicious file deletion attempts
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface (System > Status) or CLI 'show version' commandCheck Version:
show versionVerify Fix Applied:
Confirm firmware version is 10.2.1.0-18sv or later and test path traversal attempts are blocked📡 Detection & Monitoring
Log Indicators:
- Unauthenticated file deletion attempts
- Path traversal patterns in web logs
- System reboot events
Network Indicators:
- HTTP requests with ../ patterns to SMA100 interface
- Unauthenticated access to administrative endpoints
SIEM Query:
source="SMA100" AND (uri="*../*" OR action="delete") AND auth_status="failed"🔗 References
- http://packetstormsecurity.com/files/164564/SonicWall-SMA-10.2.1.0-17sv-Password-Reset.html
- https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0021
- http://packetstormsecurity.com/files/164564/SonicWall-SMA-10.2.1.0-17sv-Password-Reset.html
- https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0021
