CVE-2023-4542: D-Link DAR-8000-10 Firmware RCE Flaw

CVE-2023-4542 Overview

A critical OS command injection vulnerability has been discovered in D-Link DAR-8000-10 network devices running firmware versions up to 20230809. The vulnerability exists in the /app/sys1.php file, where the cmd parameter is insufficiently validated, allowing remote attackers to execute arbitrary operating system commands on the affected device. This vulnerability can be exploited remotely without requiring authentication, making it particularly dangerous for exposed network infrastructure.

Critical Impact

Remote attackers can execute arbitrary commands with device-level privileges, potentially leading to complete device compromise, network infiltration, data exfiltration, and use of the device as a pivot point for further attacks.

Affected Products

• D-Link DAR-8000-10 Firmware (versions up to 20230809)
• D-Link DAR-8000-10 Hardware

Discovery Timeline

• 2023-08-25 - CVE-2023-4542 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-4542

Vulnerability Analysis

This vulnerability is classified as CWE-78 (Improper Neutralization of Special Elements used in an OS Command), commonly known as OS Command Injection. The vulnerability exists in the web management interface of the D-Link DAR-8000-10 device, specifically within the /app/sys1.php script.

The vulnerable endpoint accepts user-controlled input through the cmd parameter without proper sanitization or validation. When an attacker supplies a malicious payload such as id (or other system commands), the input is passed directly to the underlying operating system shell for execution. This allows attackers to run arbitrary commands with the privileges of the web server process, which typically runs with elevated permissions on embedded network devices.

The attack can be initiated remotely over the network without requiring any authentication credentials, and the user interaction requirement is minimal. The exploit has been publicly disclosed and documented, significantly increasing the risk of exploitation in the wild.

Root Cause

The root cause of this vulnerability is the failure to properly sanitize user-supplied input in the cmd parameter before passing it to system-level command execution functions. The /app/sys1.php script directly concatenates or passes the user input to shell commands without implementing input validation, allowlisting, or proper escaping mechanisms. This represents a fundamental secure coding failure where untrusted data is allowed to influence command execution.

Attack Vector

The attack vector is network-based, targeting the web management interface of the D-Link DAR-8000-10 device. An attacker can craft a malicious HTTP request to the /app/sys1.php endpoint with a specially crafted cmd parameter containing OS commands. The vulnerability allows for unauthenticated remote exploitation, meaning any attacker with network access to the device's management interface can potentially compromise it.

A typical attack scenario involves sending an HTTP request with command injection payloads such as command chaining operators (;, &&, ||) or command substitution syntax to execute arbitrary system commands. For example, supplying id as the cmd parameter value demonstrates command execution by returning the current user context.

For detailed technical exploitation information, refer to the GitHub RCE Documentation maintained by security researchers.

Detection Methods for CVE-2023-4542

Indicators of Compromise

• Unusual HTTP requests to /app/sys1.php containing suspicious cmd parameter values
• Unexpected outbound network connections from D-Link DAR-8000-10 devices
• Presence of unauthorized user accounts or modified system configurations on the device
• Anomalous process execution or shell activity on the affected network appliance

Detection Strategies

• Implement network-based intrusion detection rules to identify HTTP requests targeting /app/sys1.php with command injection patterns
• Monitor web server access logs for requests containing shell metacharacters (;, |, $(), backticks) in parameter values
• Deploy SentinelOne Singularity to detect and block command injection attempts and post-exploitation activities
• Use web application firewall (WAF) rules to filter malicious requests targeting the vulnerable endpoint

Monitoring Recommendations

• Enable verbose logging on D-Link devices and forward logs to a centralized SIEM for analysis
• Monitor for unusual authentication attempts or configuration changes on network devices
• Implement network segmentation to limit exposure of device management interfaces
• Regularly audit network device inventory to identify vulnerable D-Link DAR-8000-10 installations

How to Mitigate CVE-2023-4542

Immediate Actions Required

• Immediately restrict network access to the D-Link DAR-8000-10 management interface using firewall rules
• Isolate affected devices from critical network segments until patching is complete
• Audit device configurations for signs of compromise or unauthorized changes
• Enable additional monitoring and logging for traffic to and from affected devices

Patch Information

The vendor (D-Link) was contacted early about this disclosure but did not respond. As of the last update, no official patch has been released by D-Link. Organizations should monitor D-Link's official security advisories for future firmware updates. Additional vulnerability details are available at VulDB #238047 and VulDB CTI #238047.

Workarounds

• Disable remote management access or restrict it to trusted IP addresses only via access control lists (ACLs)
• Place the device management interface behind a VPN to prevent direct internet exposure
• Implement network segmentation to isolate vulnerable devices from sensitive network resources
• Consider replacing vulnerable devices with supported alternatives if no patch becomes available

# Example: Restrict management interface access using iptables
# Allow management access only from trusted admin network
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP