CVE-2023-29665
📋 TL;DR
CVE-2023-29665 is a critical stack overflow vulnerability in D-Link DIR823G routers that allows remote attackers to execute arbitrary code by sending specially crafted requests to the SetPasswdSettings HNAP endpoint. This affects all users of DIR823G routers running vulnerable firmware versions, potentially giving attackers full control of the device. The vulnerability is remotely exploitable without authentication.
💻 Affected Systems
- D-Link DIR823G
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise leading to persistent backdoor installation, network traffic interception, credential theft, and use as a pivot point to attack internal networks.
Likely Case
Remote code execution allowing attackers to modify router settings, intercept traffic, deploy malware, or join botnets.
If Mitigated
Limited impact if device is behind firewall with restricted WAN access, though internal attackers could still exploit.
🎯 Exploit Status
Proof-of-concept code is publicly available on GitHub. The exploit requires sending a specially crafted HTTP POST request to the vulnerable endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check D-Link security bulletin for latest patched version
Vendor Advisory: https://www.dlink.com/en/security-bulletin/
Restart Required: Yes
Instructions:
1. Log into D-Link support portal. 2. Download latest firmware for DIR823G. 3. Access router web interface. 4. Navigate to System Tools > Firmware Upgrade. 5. Upload and apply new firmware. 6. Reboot router after completion.
🔧 Temporary Workarounds
Disable Remote Management
allPrevent external access to router management interface
Access router web interface > Advanced > Remote Management > Disable
Block HNAP Ports
linuxBlock access to HNAP protocol ports on firewall
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
iptables -A INPUT -p tcp --dport 8080 -j DROP
🧯 If You Can't Patch
- Isolate router on separate VLAN with strict firewall rules
- Implement network segmentation to limit router's access to critical systems
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router web interface under Status > Device Info. If version is V1.0.2B05 or earlier, device is vulnerable.Check Version:
curl -s http://router-ip/HNAP1/ | grep -i version or check web interfaceVerify Fix Applied:
After firmware update, verify version shows patched release. Test by attempting to send crafted request to /HNAP1/ endpoint (not recommended on production).📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /HNAP1/
- Multiple failed authentication attempts followed by SetPasswdSettings requests
- Large payloads sent to HNAP endpoints
Network Indicators:
- HTTP POST requests to /HNAP1/ with oversized NewPassword parameter
- Traffic to router on ports 80/443/8080 from unexpected sources
SIEM Query:
source="router_logs" AND (uri="/HNAP1/" AND method="POST" AND (param="NewPassword" OR data_size>1000))