CVE-2021-20017
📋 TL;DR
This CVE describes a post-authentication command injection vulnerability in SonicWall SMA100 appliances. An authenticated attacker can execute arbitrary operating system commands with 'nobody' user privileges. This affects SMA100 version 10.2.0.5 and earlier.
💻 Affected Systems
- SonicWall SMA100
📦 What is this software?
Sma100 Firmware by Sonicwall
⚠️ Risk & Real-World Impact
Worst Case
An authenticated attacker gains remote code execution, potentially leading to lateral movement, data exfiltration, or installation of persistent backdoors.
Likely Case
Authenticated attackers execute commands to gather system information, modify configurations, or establish footholds for further attacks.
If Mitigated
With proper network segmentation and access controls, impact is limited to the SMA100 appliance itself.
🎯 Exploit Status
Exploitation requires valid credentials but is straightforward once authenticated.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 10.2.0.6 or later
Vendor Advisory: https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0004
Restart Required: Yes
Instructions:
1. Download SMA100 firmware version 10.2.0.6 or later from MySonicWall. 2. Log into SMA100 web interface. 3. Navigate to System > Settings > Firmware Upgrade. 4. Upload and install the new firmware. 5. Reboot the appliance.
🔧 Temporary Workarounds
Restrict Network Access
allLimit access to SMA100 management interface to trusted IP addresses only.
Enforce Strong Authentication
allImplement multi-factor authentication and strong password policies for SMA100 accounts.
🧯 If You Can't Patch
- Isolate SMA100 appliance in a dedicated network segment with strict firewall rules.
- Implement network monitoring and alerting for suspicious commands or unusual authentication patterns.
🔍 How to Verify
Check if Vulnerable:
Check SMA100 firmware version in web interface under System > Settings > Firmware Upgrade.Check Version:
ssh admin@[SMA100_IP] show versionVerify Fix Applied:
Confirm firmware version is 10.2.0.6 or later in System > Settings > Firmware Upgrade.📡 Detection & Monitoring
Log Indicators:
- Unusual command execution patterns in system logs
- Multiple failed login attempts followed by successful authentication
- Suspicious process creation by 'nobody' user
Network Indicators:
- Unusual outbound connections from SMA100 appliance
- Traffic to unexpected ports or IP addresses
SIEM Query:
source="SMA100" AND (event_type="command_execution" OR user="nobody")