CVE-2021-20019
📋 TL;DR
CVE-2021-20019 is a memory disclosure vulnerability in SonicOS HTTP servers where crafted HTTP requests can leak partial memory contents. This could expose sensitive internal data like credentials, session tokens, or configuration details. Organizations using affected SonicWall firewall appliances are vulnerable.
💻 Affected Systems
- SonicWall firewalls with SonicOS
📦 What is this software?
Sonicos by Sonicwall
Sonicos by Sonicwall
Sonicos by Sonicwall
Sonicos by Sonicwall
Sonicos by Sonicwall
Sonicosv by Sonicwall
⚠️ Risk & Real-World Impact
Worst Case
Attackers could extract sensitive memory contents including administrative credentials, VPN keys, or network configuration data, leading to full network compromise.
Likely Case
Attackers could obtain partial memory data that might contain session tokens or configuration fragments, potentially enabling further attacks.
If Mitigated
With proper network segmentation and access controls, impact is limited to potential information disclosure without direct system compromise.
🎯 Exploit Status
Exploitation requires sending crafted HTTP requests to the management interface. No authentication is required if HTTP management is exposed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: SonicOS 7.0.1-5050, 6.5.4.4-44v-21-1452, and later versions
Vendor Advisory: https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0006
Restart Required: Yes
Instructions:
1. Log into SonicWall management interface. 2. Navigate to System > Settings > Firmware. 3. Download and install the latest firmware version. 4. Reboot the firewall after installation completes.
🔧 Temporary Workarounds
Disable HTTP Management
allDisable HTTP access to the management interface and use HTTPS only
Navigate to System > Administration > Management > HTTP/HTTPS and disable HTTP
Restrict Management Access
allLimit management interface access to trusted IP addresses only
Navigate to System > Administration > Management > Access Rule and configure IP restrictions
🧯 If You Can't Patch
- Implement strict network segmentation to isolate SonicWall management interfaces
- Deploy network monitoring and intrusion detection for anomalous HTTP requests to management interfaces
🔍 How to Verify
Check if Vulnerable:
Check SonicOS version via web interface: System > Status > System Status or CLI: show versionCheck Version:
show versionVerify Fix Applied:
Verify firmware version is equal to or newer than patched versions listed in vendor advisory📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP requests to management interface
- Multiple failed or malformed HTTP requests
Network Indicators:
- HTTP requests with unusual headers or parameters to firewall management IP
SIEM Query:
source_ip=* AND dest_ip=firewall_management_ip AND http_method=GET AND (http_uri contains unusual_pattern OR http_user_agent contains exploit_tool)