CVE-2024-39202 Overview
CVE-2024-39202 is a remote command execution vulnerability affecting the D-Link DIR-823X AX3000 router running firmware version 240126. The flaw resides in the /goform/set_lan_settings endpoint, which fails to sanitize the dhcpd_startip parameter before passing it to a shell context. An authenticated attacker on the network can inject operating system commands that execute with the privileges of the web management process, typically root on embedded devices. Successful exploitation results in full device compromise, including persistent access, traffic interception, and pivoting into internal networks. The vulnerability is classified under CWE-78: Improper Neutralization of Special Elements used in an OS Command.
Critical Impact
Attackers gain root-level command execution on affected DIR-823X routers, enabling complete device takeover and lateral movement into protected networks.
Affected Products
- D-Link DIR-823X AX3000 firmware version 240126
- D-Link DIR-823X AX3000 hardware
- Deployments exposing the LAN settings web interface
Discovery Timeline
- 2024-07-08 - CVE-2024-39202 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-39202
Vulnerability Analysis
The vulnerability originates in the LAN configuration handler exposed at /goform/set_lan_settings. This endpoint accepts a dhcpd_startip parameter that defines the starting IP of the DHCP address pool. The handler passes the value directly into a shell command, likely through a system() or popen() call used to reconfigure the DHCP daemon.
Because the parameter is not validated or escaped, an attacker can append shell metacharacters such as ;, |, or backticks to inject arbitrary commands. The injected commands execute in the same context as the router's HTTP daemon, which runs as root on the DIR-823X platform.
The CWE-78 classification confirms the root cause as OS command injection. A public proof of concept is available through a GitHub Gist published by researcher Swind1er, lowering the barrier to weaponization.
Root Cause
The firmware constructs shell commands by concatenating attacker-controlled input from HTTP POST bodies. The dhcpd_startip value flows into a shell invocation without input filtering, allow-list validation, or use of safer APIs such as execve() with argument arrays. This design pattern is common in low-cost SOHO routers where CGI handlers wrap busybox utilities.
Attack Vector
Exploitation requires network access to the router's management interface and low-privilege authentication. An attacker sends a crafted HTTP POST request to /goform/set_lan_settings with a malicious payload embedded in the dhcpd_startip field. The injected commands execute immediately when the backend service applies the LAN configuration. No user interaction is required, and the attack completes in a single request.
See the public proof-of-concept for the specific request format and payload structure.
Detection Methods for CVE-2024-39202
Indicators of Compromise
- HTTP POST requests to /goform/set_lan_settings containing shell metacharacters (;, |, &, backticks, $()) in the dhcpd_startip field
- Unexpected outbound connections originating from the router's WAN interface to unfamiliar hosts
- New or modified files in writable firmware locations such as /tmp, /var, or /etc
- Presence of unauthorized processes such as reverse shells, telnetd instances, or scripts launched by the HTTP daemon
Detection Strategies
- Inspect router HTTP access logs for POST requests targeting /goform/set_lan_settings with non-IPv4-formatted values in dhcpd_startip
- Deploy network intrusion detection signatures that flag command injection patterns in traffic destined for router management interfaces
- Baseline expected DHCP configuration changes and alert on out-of-band modifications
Monitoring Recommendations
- Aggregate router syslog output to a central log platform and monitor for authentication events followed by configuration changes
- Monitor for unusual DNS queries or outbound traffic patterns from the router itself
- Track firmware integrity by comparing running versions against known-good baselines
How to Mitigate CVE-2024-39202
Immediate Actions Required
- Restrict access to the router's web management interface to trusted management VLANs or specific administrative hosts only
- Change default and weak administrator credentials to reduce the risk of authenticated exploitation
- Disable remote WAN-side administration if it is currently enabled
- Audit existing DHCP and LAN configurations for signs of tampering or injected commands
Patch Information
At the time of publication, no vendor advisory or firmware update is listed in the NVD entry for CVE-2024-39202. Administrators should monitor the D-Link Security Advisories page for updates specific to the DIR-823X AX3000 platform. If the vendor does not publish a fix, consider replacing affected units with actively supported models.
Workarounds
- Place affected routers behind a network segment that restricts inbound access to the management interface
- Enforce strong, unique credentials on all administrative accounts to limit low-privilege authenticated access required for exploitation
- Disable the web administration service when not actively in use if the firmware supports scheduled service control
# Example: restrict router management access using an upstream firewall (iptables)
# Allow only a dedicated management host to reach the router's HTTP interface
iptables -A FORWARD -s 192.0.2.10 -d 192.168.0.1 -p tcp --dport 80 -j ACCEPT
iptables -A FORWARD -d 192.168.0.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.0.1 -p tcp --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
