CVE-2021-28203
📋 TL;DR
This vulnerability allows remote attackers with administrator access to ASUS BMC firmware to execute arbitrary commands via command injection in the Web Set Media Image function. It affects ASUS Baseboard Management Controller (BMC) firmware used for server management. Attackers can gain full control of affected systems.
💻 Affected Systems
- ASUS BMC firmware
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to install persistent backdoors, exfiltrate sensitive data, or use the system as a pivot point to attack other network resources.
Likely Case
Attackers with administrator credentials can execute arbitrary commands to disrupt operations, steal credentials, or deploy malware on the managed server.
If Mitigated
With proper network segmentation and access controls, impact is limited to the BMC interface without affecting the main server operating system.
🎯 Exploit Status
Exploitation requires administrator credentials but is straightforward once authenticated. No public exploit code is referenced in the provided advisories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified in references; check ASUS advisories for exact version
Vendor Advisory: https://www.asus.com/content/ASUS-Product-Security-Advisory/
Restart Required: Yes
Instructions:
1. Check ASUS security advisory for affected products. 2. Download updated BMC firmware from ASUS support site. 3. Apply firmware update through BMC web interface or management tools. 4. Reboot the BMC and verify the update.
🔧 Temporary Workarounds
Restrict BMC Network Access
allLimit access to BMC management interface to trusted administrative networks only
Configure firewall rules to restrict access to BMC IP/port (typically 443/HTTPS)
Implement Strong Authentication
allUse complex, unique passwords for BMC administrator accounts and enable multi-factor authentication if supported
🧯 If You Can't Patch
- Isolate BMC management network from production and internet-facing networks
- Monitor BMC access logs for unauthorized authentication attempts and command execution patterns
🔍 How to Verify
Check if Vulnerable:
Check BMC firmware version against ASUS security advisory. If version is older than patched release, system is vulnerable.Check Version:
Check BMC web interface → System Information → Firmware Version, or use IPMI command: ipmitool mc infoVerify Fix Applied:
Verify BMC firmware version matches or exceeds the patched version specified in ASUS advisory.📡 Detection & Monitoring
Log Indicators:
- Unusual authentication patterns to BMC web interface
- Command execution logs in BMC system logs
- Multiple failed login attempts followed by successful login
Network Indicators:
- Unexpected outbound connections from BMC management interface
- Traffic patterns indicating command injection attempts
SIEM Query:
source="bmc_logs" AND (event="command_execution" OR event="authentication_success" from unusual IP)🔗 References
- https://www.asus.com/content/ASUS-Product-Security-Advisory/
- https://www.asus.com/tw/support/callus/
- https://www.twcert.org.tw/tw/cp-132-4573-aa336-1.html
- https://www.asus.com/content/ASUS-Product-Security-Advisory/
- https://www.asus.com/tw/support/callus/
- https://www.twcert.org.tw/tw/cp-132-4573-aa336-1.html
