CVE-2021-20049
📋 TL;DR
CVE-2021-20049 is a username enumeration vulnerability in SonicWall SMA100's password change API that allows unauthenticated attackers to determine valid usernames by analyzing server responses. This affects organizations using vulnerable SMA100 appliances for remote access. The vulnerability enables reconnaissance that can facilitate credential attacks.
💻 Affected Systems
- SonicWall SMA100 Series
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers enumerate all valid usernames, then conduct targeted password attacks leading to unauthorized access to the SMA100 portal and potentially internal network resources.
Likely Case
Attackers identify valid usernames and use them for phishing campaigns or targeted credential stuffing attacks against the SMA100 portal.
If Mitigated
With proper network segmentation and monitoring, enumeration attempts are detected and blocked before credential attacks succeed.
🎯 Exploit Status
The vulnerability is simple to exploit via HTTP requests to the password change endpoint with different usernames.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 10.2.1.5-29sv or later
Vendor Advisory: https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0030
Restart Required: Yes
Instructions:
1. Download the latest firmware from MySonicWall portal. 2. Backup current configuration. 3. Upload and install the firmware update. 4. Reboot the appliance.
🔧 Temporary Workarounds
Restrict API Access
allBlock external access to the SMA100 password change API using firewall rules or network segmentation.
🧯 If You Can't Patch
- Implement network segmentation to restrict SMA100 access to trusted IP ranges only
- Enable multi-factor authentication for all SMA100 user accounts
🔍 How to Verify
Check if Vulnerable:
Check firmware version via SMA100 web interface: System > Status > Firmware VersionCheck Version:
ssh admin@smagw show versionVerify Fix Applied:
Verify firmware version is 10.2.1.5-29sv or later and test username enumeration is no longer possible📡 Detection & Monitoring
Log Indicators:
- Multiple failed password change attempts with different usernames from single source IP
- Unusual patterns of requests to /cgi-bin/passchange.cgi
Network Indicators:
- HTTP POST requests to SMA100 password change endpoint from untrusted sources
- Rapid sequential username attempts
SIEM Query:
source="SMA100" AND (uri="/cgi-bin/passchange.cgi" OR method="POST") | stats count by src_ip