CVE-2021-44881
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary commands on affected D-Link DIR-882 routers via a crafted HNAP1 POST request to the twsystem function. Attackers can gain full control of the device without authentication. Only users of specific D-Link DIR-882 firmware versions are affected.
💻 Affected Systems
- D-Link DIR-882
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the router allowing attackers to install persistent malware, intercept all network traffic, pivot to internal networks, and use the device as part of a botnet.
Likely Case
Router takeover leading to DNS hijacking, credential theft from network traffic, and use as a proxy for malicious activities.
If Mitigated
Limited impact if device is behind firewall with restricted WAN access, though internal threats remain possible.
🎯 Exploit Status
Proof of concept code is publicly available. Exploitation requires sending a specially crafted HTTP POST request to the HNAP1 endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check D-Link support for latest firmware
Vendor Advisory: https://supportannouncement.us.dlink.com/announcement/publication.aspx?name=SAP10287
Restart Required: Yes
Instructions:
1. Log into D-Link support portal. 2. Download latest firmware for DIR-882. 3. Access router admin interface. 4. Navigate to firmware update section. 5. Upload and install new firmware. 6. Reboot router.
🔧 Temporary Workarounds
Disable remote management
allPrevent external access to router web interface
Access router admin > Advanced > Remote Management > Disable
Restrict admin access
allLimit admin interface access to specific IP addresses
Access router admin > Advanced > Firewall > Add rule to restrict admin port (typically 80/443) to trusted IPs
🧯 If You Can't Patch
- Place router behind a firewall that blocks all inbound traffic to router admin ports (80, 443, 8080)
- Implement network segmentation to isolate router from critical internal systems
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router admin interface under Maintenance > Firmware. If version is DIR_882_FW1.30B06_Hotfix_02, device is vulnerable.Check Version:
curl -s http://router-ip/GetDeviceSettings | grep FirmwareVersionVerify Fix Applied:
After updating, verify firmware version shows a newer version than DIR_882_FW1.30B06_Hotfix_02.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /HNAP1/ endpoints
- Commands like 'telnet', 'wget', 'curl' in web logs
- Multiple failed login attempts followed by successful command execution
Network Indicators:
- Unexpected outbound connections from router
- DNS queries to suspicious domains
- Traffic to known exploit servers
SIEM Query:
source="router-logs" AND (url="/HNAP1/*" AND method="POST" AND (user_agent="curl" OR user_agent="wget" OR body CONTAINS "system"))🔗 References
- https://github.com/pjqwudi/my_vuln/blob/main/D-link/vuln_3/3.md
- https://supportannouncement.us.dlink.com/announcement/publication.aspx?name=SAP10287
- https://www.dlink.com/en/security-bulletin/
- https://github.com/pjqwudi/my_vuln/blob/main/D-link/vuln_3/3.md
- https://supportannouncement.us.dlink.com/announcement/publication.aspx?name=SAP10287
- https://www.dlink.com/en/security-bulletin/
