Can you explain this vulnerability to me?

CVE-2026-8346 is a stored command injection vulnerability found in the D-Link DIR-816A2 router firmware version 1.10CNB05_R1B011D88210. It affects the port forwarding function, specifically the handling of the ip_address parameter.

The vulnerability arises because the ip_address input is only lightly validated to check if it looks like an IP address, but it does not filter out dangerous command characters. This input is then stored in the router's configuration (NVRAM) without proper cleaning.

Later, when the router applies firewall rules, it reads this stored ip_address and uses it directly in a system command to configure iptables. Because the input was not sanitized, an attacker can inject arbitrary shell commands through the ip_address field.

This allows an authenticated attacker to execute commands on the router with root privileges remotely by manipulating the port forwarding ip_address parameter.

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How can this vulnerability impact me? :

This vulnerability can have serious impacts because it allows an attacker with authentication to execute arbitrary commands on the router with root privileges.

• Remote command execution can lead to full control over the router.
• Attackers can modify network configurations, intercept or redirect traffic, or create persistent backdoors.
• It can compromise the security and privacy of all devices connected to the affected network.
• The exploit is publicly available, increasing the risk of widespread attacks.

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How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability can be detected by checking if the D-Link DIR-816 router firmware version 1.10CNB05_R1B011D88210 is running and if the port forwarding functionality is accessible. Specifically, the vulnerability exists in the `goform/portForward` handler where the `ip_address` parameter is processed without proper sanitization.

To detect exploitation attempts or test for the vulnerability, you can try sending crafted HTTP POST requests to the router's `goform/portForward` endpoint with malicious payloads in the `ip_address` parameter to see if command injection is possible.

Example commands to test or detect the vulnerability might include using curl to send a payload that attempts to inject shell commands:

• curl -X POST http://<router-ip>/goform/portForward -d "ip_address=8.8.8.8;id"
• curl -X POST http://<router-ip>/goform/portForward -d "ip_address=8.8.8.8;cat /etc/passwd"

Monitoring the router's firewall rules or NVRAM configuration for unexpected or suspicious entries in the port forwarding rules may also help detect exploitation.

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What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation steps include restricting access to the router's management interface to trusted users only, preferably limiting it to local network access and disabling remote management if enabled.

Avoid using or configuring port forwarding rules that accept untrusted input for the IP address field until a firmware update or patch is applied.

Check for and apply any available firmware updates from D-Link that address this vulnerability.

If possible, reset the router to factory defaults to clear any maliciously injected port forwarding rules.

Monitor network traffic and router logs for signs of exploitation attempts.

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