CVE-2025-9026: D-Link DIR-860L Firmware RCE Vulnerability

CVE-2025-9026 Overview

A command injection vulnerability has been identified in D-Link DIR-860L firmware version 2.04.B04. This vulnerability affects the ssdpcgi_main function within the htdocs/cgibin file, which is part of the Simple Service Discovery Protocol (SSDP) component. The flaw allows remote attackers to inject and execute arbitrary operating system commands on the affected device through improper input handling.

Critical Impact

This vulnerability enables remote OS command injection on end-of-life D-Link DIR-860L routers with no vendor patch available, potentially allowing attackers to gain full control of the device.

Affected Products

• D-Link DIR-860L Firmware version 2.04.B04
• D-Link DIR-860L Hardware (all revisions running vulnerable firmware)

Discovery Timeline

• 2025-08-15 - CVE-2025-9026 published to NVD
• 2025-08-18 - Last updated in NVD database

Technical Details for CVE-2025-9026

Vulnerability Analysis

This vulnerability exists in the Simple Service Discovery Protocol (SSDP) implementation of the D-Link DIR-860L router. The ssdpcgi_main function located in htdocs/cgibin fails to properly sanitize user-supplied input before passing it to system command execution routines. This lack of input validation enables attackers to inject arbitrary commands that are then executed with the privileges of the web server process, typically running as root on embedded devices.

The vulnerability is classified as CWE-77 (Improper Neutralization of Special Elements used in a Command), commonly known as command injection. An attacker can exploit this remotely over the network without requiring authentication, making it particularly dangerous for devices exposed to the internet. The exploit has been publicly disclosed, increasing the risk of active exploitation in the wild.

Importantly, this vulnerability affects a product that has reached end-of-life status and is no longer supported by D-Link, meaning no official security patch will be released.

Root Cause

The root cause of this vulnerability is improper input validation and sanitization in the ssdpcgi_main function. User-controlled input processed by the SSDP handler is concatenated directly into system command strings without adequate filtering of shell metacharacters or command separators. This allows attackers to break out of the intended command context and inject their own commands.

Attack Vector

The attack can be initiated remotely over the network. An attacker sends specially crafted SSDP requests to the vulnerable device's web interface. By including shell metacharacters (such as ;, |, &&, or backticks) followed by malicious commands in the request parameters, the attacker can achieve arbitrary command execution on the underlying operating system.

The vulnerability is accessible without authentication, and due to the network-based attack vector, any DIR-860L device reachable over a network (including the internet if exposed) is potentially vulnerable. Given that the exploit has been publicly disclosed, attackers have access to the technical details needed to craft successful exploitation attempts.

Detection Methods for CVE-2025-9026

Indicators of Compromise

• Unusual outbound network connections from the router to unknown external IP addresses
• Unexpected processes running on the device that are not part of normal firmware operation
• Modified system files or new files appearing in writable directories
• DNS settings changed to redirect traffic to malicious servers
• Unexpected reboots or performance degradation of the router

Detection Strategies

• Monitor network traffic for anomalous SSDP requests containing shell metacharacters such as ;, |, &&, or backtick characters
• Implement network intrusion detection signatures to identify command injection patterns in HTTP requests to the router's CGI endpoints
• Use network segmentation to isolate end-of-life devices and monitor traffic crossing segment boundaries
• Deploy logging solutions to capture and analyze all requests to the router's web interface

Monitoring Recommendations

• Enable and review router access logs if available for suspicious request patterns targeting /htdocs/cgibin
• Monitor for outbound connections on uncommon ports that may indicate reverse shell activity
• Set up alerts for any configuration changes on the router, particularly DNS and firewall settings
• Conduct periodic integrity checks of the router's configuration against a known-good baseline

How to Mitigate CVE-2025-9026

Immediate Actions Required

• Replace the D-Link DIR-860L with a currently supported router model that receives security updates
• If immediate replacement is not possible, restrict network access to the router's management interface to trusted internal networks only
• Disable UPnP and SSDP services on the router if such options are available in the configuration
• Ensure the router's management interface is not exposed to the internet
• Implement network-level access controls to limit which hosts can communicate with the router

Patch Information

D-Link has confirmed that the DIR-860L has reached end-of-life status and is no longer supported. No official security patch will be released for this vulnerability. Users are strongly advised to replace the affected device with a currently supported model. For additional information, refer to the D-Link Security Resources page.

Additional technical details about this vulnerability can be found in the GitHub Issue CVE-17 and the VulDB entry.

Workarounds

• Implement strict firewall rules at the network perimeter to block external access to SSDP ports (typically UDP 1900) and the router's web management interface
• Place the vulnerable device behind a separate firewall or in an isolated network segment with restricted access
• Disable remote management features and only allow local administration if possible
• Consider deploying a network-based web application firewall (WAF) or intrusion prevention system (IPS) to filter malicious requests targeting the vulnerable endpoint
• Monitor for and block any suspicious traffic patterns indicative of command injection attempts