CVE-2026-2175: D-Link DIR-823X Firmware RCE Vulnerability

CVE-2026-2175 Overview

A critical OS command injection vulnerability has been identified in the D-Link DIR-823X router firmware version 250416. This vulnerability affects the function sub_420618 within the /goform/set_upnp endpoint, where improper handling of the upnp_enable argument allows an attacker to inject and execute arbitrary operating system commands. Remote exploitation of this vulnerability is possible, and exploit details have been made publicly available, increasing the risk of active exploitation.

Critical Impact

Authenticated attackers can achieve remote code execution on affected D-Link DIR-823X routers by injecting malicious OS commands through the UPnP configuration interface, potentially leading to complete device compromise and network infiltration.

Affected Products

• D-Link DIR-823X Firmware version 250416
• D-Link DIR-823X Hardware

Discovery Timeline

• February 8, 2026 - CVE-2026-2175 published to NVD
• February 11, 2026 - Last updated in NVD database

Technical Details for CVE-2026-2175

Vulnerability Analysis

This vulnerability represents a classic OS command injection flaw (CWE-78) combined with improper neutralization of special elements used in a command (CWE-77). The vulnerable function sub_420618 processes user-supplied input from the upnp_enable parameter without adequate sanitization or validation. When a user submits a request to the /goform/set_upnp endpoint, the application fails to properly escape or filter special characters that could be interpreted as command delimiters or operators by the underlying shell.

The attack requires network access and high privileges (authenticated access to the router's administrative interface). Once authenticated, an attacker can craft a malicious request containing shell metacharacters within the upnp_enable parameter. These characters are passed directly to system functions that execute shell commands, allowing the injected payload to run with the privileges of the router's web service process—typically root on embedded devices.

Root Cause

The root cause of CVE-2026-2175 lies in the absence of proper input validation and output encoding within the sub_420618 function. The firmware directly incorporates user-controlled data from the upnp_enable parameter into a command string that is subsequently executed by the system shell. This design flaw violates fundamental secure coding principles by trusting user input implicitly, creating a direct path from HTTP request parameters to OS command execution.

Attack Vector

The attack vector is network-based, requiring the attacker to have authenticated access to the device's administrative web interface. The exploitation path follows these steps:

1. Attacker authenticates to the D-Link DIR-823X administrative interface
2. Attacker sends a crafted POST request to /goform/set_upnp
3. The upnp_enable parameter contains malicious command injection payload
4. The sub_420618 function processes the input without sanitization
5. Injected commands execute with system privileges on the router

The vulnerability allows attackers to execute arbitrary commands, potentially enabling persistent access, network reconnaissance, traffic interception, or using the compromised device as a pivot point for further attacks within the network. Technical details and proof-of-concept information are available through the GitHub CVE Issue Discussion.

Detection Methods for CVE-2026-2175

Indicators of Compromise

• Unusual HTTP POST requests to /goform/set_upnp containing shell metacharacters (;, |, $(), backticks) in the upnp_enable parameter
• Unexpected outbound network connections from the router to external IP addresses
• Unauthorized processes or services running on the device that were not present in baseline configurations
• Modified router configuration files or the presence of unauthorized user accounts

Detection Strategies

• Implement network intrusion detection rules to identify HTTP requests to /goform/set_upnp containing command injection patterns
• Deploy web application firewall (WAF) rules to block requests with shell metacharacters in form parameters destined for router management interfaces
• Monitor router logs for repeated authentication attempts followed by UPnP configuration changes
• Use SentinelOne Singularity for network visibility to detect anomalous traffic patterns originating from IoT devices

Monitoring Recommendations

• Establish baseline network behavior for D-Link DIR-823X devices and alert on deviations
• Configure SIEM rules to correlate authentication events with subsequent POST requests to vulnerable endpoints
• Implement continuous firmware integrity monitoring to detect unauthorized modifications
• Review router access logs regularly for signs of exploitation attempts or successful compromise

How to Mitigate CVE-2026-2175

Immediate Actions Required

• Restrict administrative interface access to trusted IP addresses only using firewall rules
• Disable remote administration if not strictly required for business operations
• Ensure strong, unique credentials are configured for all administrative accounts
• Isolate affected D-Link DIR-823X devices on a separate network segment until patching is possible

Patch Information

As of the last NVD update on February 11, 2026, no official patch has been released by D-Link for this vulnerability. Organizations should monitor the D-Link Security Information page for firmware updates addressing CVE-2026-2175. Additional vulnerability details can be found at VulDB #344876.

Workarounds

• Disable the UPnP functionality entirely if not required for network operations
• Implement network-level access controls to prevent untrusted users from reaching the router's administrative interface
• Consider deploying a firewall or intrusion prevention system in front of the vulnerable device to filter malicious requests
• Evaluate replacing end-of-life or unsupported devices with actively maintained alternatives that receive regular security updates