CVE-2026-4465: D-Link DIR-513 RCE Vulnerability

CVE-2026-4465 Overview

A critical OS command injection vulnerability has been identified in D-Link DIR-513 firmware version 1.10. The vulnerability exists in an unknown function within the /goform/formSysCmd file, where improper handling of the sysCmd argument allows attackers to inject and execute arbitrary operating system commands. This flaw can be exploited remotely, and proof-of-concept exploit code has been publicly disclosed. Notably, this vulnerability affects a product that has reached end-of-life status and is no longer supported by D-Link.

Critical Impact

Remote attackers can execute arbitrary OS commands on affected D-Link DIR-513 routers, potentially leading to complete device compromise, network infiltration, and use of the device in botnet operations.

Affected Products

• D-Link DIR-513 firmware version 1.10
• D-Link DIR-513 (End-of-Life product - no longer supported)

Discovery Timeline

• 2026-03-20 - CVE-2026-4465 published to NVD
• 2026-03-20 - Last updated in NVD database

Technical Details for CVE-2026-4465

Vulnerability Analysis

This vulnerability is classified as CWE-77 (Command Injection), which occurs when an application constructs all or part of an OS command using externally-influenced input without properly neutralizing special elements. In the case of the D-Link DIR-513, the web management interface exposes the /goform/formSysCmd endpoint which accepts user-supplied input via the sysCmd parameter.

The vulnerable function fails to properly sanitize or validate the input before passing it to the underlying operating system for execution. This allows an authenticated attacker with network access to craft malicious requests containing shell metacharacters and arbitrary commands that will be executed with the privileges of the web server process—typically root on embedded devices like consumer routers.

Root Cause

The root cause of this vulnerability is insufficient input validation and sanitization in the firmware's web interface handler for system commands. The formSysCmd handler directly passes user-controlled input to shell execution functions without filtering dangerous characters such as semicolons, pipes, backticks, or command substitution sequences. This is a common vulnerability pattern in embedded device firmware where security controls are often minimal.

Attack Vector

The attack can be launched remotely over the network against the device's web management interface. An attacker who has access to the router's administrative interface (either through local network access or if the management interface is exposed to the internet) can exploit this vulnerability by sending crafted HTTP requests to the /goform/formSysCmd endpoint with malicious command sequences in the sysCmd parameter.

The network-based attack vector combined with low complexity requirements makes this vulnerability particularly dangerous for devices exposed on the internet or in environments with untrusted network users. Successful exploitation could allow attackers to establish persistent backdoor access, exfiltrate network traffic, modify DNS settings for phishing attacks, or enroll the device into IoT botnets.

The vulnerability mechanism involves the injection of OS commands through the sysCmd parameter in HTTP requests to the /goform/formSysCmd endpoint. An attacker can append shell metacharacters followed by arbitrary commands to execute code on the underlying operating system. For detailed technical analysis and proof-of-concept information, refer to the GitHub CVE Database PDF and VulDB entry #351755.

Detection Methods for CVE-2026-4465

Indicators of Compromise

• HTTP POST or GET requests to /goform/formSysCmd containing shell metacharacters (;, |, &&, ||, `, $()) in the sysCmd parameter
• Unexpected outbound connections from the router to unknown IP addresses
• Unusual process spawning or command execution logged on the device
• Modified router configuration files or DNS settings
• Presence of unauthorized user accounts or SSH keys on the device

Detection Strategies

• Deploy network intrusion detection rules to monitor for HTTP requests to /goform/formSysCmd endpoints containing command injection patterns
• Implement web application firewall rules to block requests with shell metacharacters in form parameters
• Monitor router logs for unusual administrative access patterns or configuration changes
• Use network traffic analysis to detect anomalous outbound connections from IoT devices

Monitoring Recommendations

• Enable and centralize logging from network devices to a SIEM platform
• Configure alerts for any access attempts to the /goform/formSysCmd endpoint
• Implement network segmentation to isolate IoT devices and limit lateral movement potential
• Regularly audit device configurations for unauthorized modifications

How to Mitigate CVE-2026-4465

Immediate Actions Required

• Replace affected D-Link DIR-513 routers with supported devices, as this product is end-of-life and will not receive security patches
• If immediate replacement is not possible, disable remote management access to the device
• Ensure the router's web management interface is not exposed to the internet
• Implement network segmentation to limit exposure of vulnerable devices
• Monitor for signs of compromise on affected devices

Patch Information

No patch is available. D-Link DIR-513 has reached end-of-life status and is no longer supported by the manufacturer. D-Link will not be releasing security updates for this vulnerability. The recommended mitigation is to replace the affected device with a currently supported router model.

For additional information, refer to the D-Link Official Website for supported replacement products.

Workarounds

• Disable the web management interface entirely if not required for device administration
• Restrict access to the management interface to trusted IP addresses only using firewall rules
• Place the device behind a properly configured firewall that blocks access to administrative interfaces
• Consider deploying a VPN solution to secure remote management access rather than exposing the interface directly

# Example firewall rule to restrict management interface access (on upstream firewall)
# Replace 192.168.1.1 with the router's IP and 10.0.0.0/24 with trusted management network
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -s 10.0.0.0/24 -j ACCEPT
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -s 10.0.0.0/24 -j ACCEPT
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP