CVE-2023-51621
📋 TL;DR
This vulnerability allows network-adjacent attackers with valid credentials to execute arbitrary code as root on D-Link DIR-X3260 routers. The flaw exists in the prog.cgi binary that handles HNAP requests, where improper input validation leads to a stack-based buffer overflow. Attackers on the same network can exploit this to gain complete control of affected routers.
💻 Affected Systems
- D-Link DIR-X3260
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full router compromise allowing attacker to intercept all network traffic, install persistent malware, pivot to internal networks, and disable security controls.
Likely Case
Router takeover leading to credential theft, DNS hijacking, man-in-the-middle attacks, and network disruption.
If Mitigated
Limited to authenticated attackers only, reducing exposure to compromised credentials or insider threats.
🎯 Exploit Status
Exploitation requires authentication but buffer overflow to RCE is straightforward once authenticated. ZDI has technical details but no public exploit code.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware 1.11B04
Vendor Advisory: https://supportannouncement.us.dlink.com/announcement/publication.aspx?name=SAP10365
Restart Required: Yes
Instructions:
1. Download firmware 1.11B04 from D-Link support site. 2. Log into router web interface. 3. Navigate to System Tools > Firmware Upgrade. 4. Upload the firmware file. 5. Wait for automatic reboot (do not interrupt power).
🔧 Temporary Workarounds
Disable Remote Management
allPrevent external access to web interface
Change Default Credentials
allUse strong unique passwords to reduce authentication attack surface
🧯 If You Can't Patch
- Segment router on isolated network segment with strict firewall rules
- Implement network monitoring for unusual HNAP requests to prog.cgi
🔍 How to Verify
Check if Vulnerable:
Check firmware version in web interface under Status > Device Info. If version is below 1.11B04, device is vulnerable.Check Version:
curl -k https://router-ip/status.cgi | grep FirmwareVerify Fix Applied:
Confirm firmware version shows 1.11B04 or higher after upgrade.📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts followed by HNAP POST requests to /prog.cgi
- Unusual size parameters in SetDeviceSettings requests
Network Indicators:
- HTTP POST requests to /prog.cgi with abnormally long parameter values
- HNAP SOAP requests with crafted XML to SetDeviceSettings method
SIEM Query:
source="router-logs" AND (uri="/prog.cgi" AND method="POST" AND size>1000)