CVE-2025-13562: D-Link DIR-852 Firmware RCE Vulnerability

CVE-2025-13562 Overview

A command injection vulnerability has been identified in the D-Link DIR-852 router firmware version 1.00. The vulnerability exists in the /gena.cgi endpoint, where improper handling of the service argument allows attackers to inject and execute arbitrary system commands. This vulnerability is particularly concerning as it can be exploited remotely without authentication, and the affected product has reached end-of-life status with no vendor support available.

Critical Impact
Remote attackers can execute arbitrary commands on vulnerable D-Link DIR-852 routers via the /gena.cgi endpoint, potentially leading to complete device compromise, network pivoting, and persistent unauthorized access.

Affected Products

D-Link DIR-852 Firmware version 1.00
D-Link DIR-852 Hardware (End-of-Life)

Discovery Timeline

2025-11-23 - CVE-2025-13562 published to NVD
2025-11-26 - Last updated in NVD database

Technical Details for CVE-2025-13562

Vulnerability Analysis

This vulnerability is classified under CWE-77 (Command Injection) and CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component). The flaw resides in the /gena.cgi script, which processes UPnP GENA (General Event Notification Architecture) requests on the router.

The vulnerable endpoint fails to properly sanitize the service parameter before passing it to system-level command execution functions. When a crafted HTTP request containing shell metacharacters is sent to the /gena.cgi endpoint, the malicious payload is interpreted and executed with the privileges of the web server process, typically running as root on embedded devices.

The network-accessible nature of this vulnerability means that any attacker with network access to the router's web management interface can exploit it. Since D-Link has discontinued support for this product, no official patch will be released.

Root Cause

The root cause of this vulnerability is inadequate input validation and sanitization in the CGI script handling. The service argument passed to /gena.cgi is directly concatenated into a system command string without proper escaping or validation of shell metacharacters. This allows attackers to break out of the intended command context and inject additional commands using techniques such as command chaining operators (;, &&, ||) or command substitution ($(...), backticks).

Attack Vector

The attack vector is network-based, requiring no authentication or user interaction. An attacker can craft a malicious HTTP request targeting the /gena.cgi endpoint with a specially crafted service parameter containing shell metacharacters and arbitrary commands.

The vulnerability allows remote command execution through manipulation of the service parameter in requests to the /gena.cgi endpoint. Attackers can inject shell commands using standard command injection techniques, such as appending shell metacharacters followed by arbitrary commands. Upon successful exploitation, the injected commands execute with the privileges of the web server process on the router. For detailed technical information about the exploitation mechanism, refer to the GitHub PoC Overview.

Detection Methods for CVE-2025-13562

Indicators of Compromise

Unexpected HTTP requests to /gena.cgi containing shell metacharacters (;, |, $(), backticks) in the service parameter
Unusual outbound network connections from the router to unknown IP addresses
Unexpected processes spawned by the router's web server process
Modified router configuration files or unauthorized administrative accounts

Detection Strategies

Monitor network traffic for suspicious HTTP requests targeting /gena.cgi with encoded or special characters in parameters
Implement intrusion detection rules to alert on command injection patterns in UPnP-related traffic
Review router access logs for anomalous request patterns to CGI endpoints
Deploy network monitoring to detect unusual traffic originating from router devices

Monitoring Recommendations

Enable verbose logging on network perimeter devices to capture requests to vulnerable endpoints
Implement network segmentation to isolate IoT and networking devices from critical infrastructure
Use network-based anomaly detection to identify command-and-control traffic from compromised devices
Regularly audit device firmware versions and maintain an inventory of end-of-life equipment

How to Mitigate CVE-2025-13562

Immediate Actions Required

Replace affected D-Link DIR-852 devices with currently supported router models as no patch will be provided
Disable remote management interfaces and restrict web interface access to trusted networks only
Implement network segmentation to isolate vulnerable devices from critical systems
Block external access to the router's web management interface using firewall rules
Monitor affected devices for signs of compromise until replacement can be completed

Patch Information

No patch is available for this vulnerability. D-Link has discontinued support for the DIR-852 router, and no security updates will be released. The only recommended remediation is to replace the affected device with a currently supported router model. For more information, visit the D-Link Official Website.

Workarounds

Disable UPnP functionality on the router if not required
Restrict access to the router's web management interface to specific trusted IP addresses
Place the router behind a firewall that blocks incoming connections to management ports
Consider deploying a supported firewall or router in front of the vulnerable device as an interim measure

bash

# Example firewall rules to restrict access to router management interface
# Block external access to web management (adjust interface and IP as needed)
iptables -A INPUT -i eth0 -p tcp --dport 80 -j DROP
iptables -A INPUT -i eth0 -p tcp --dport 443 -j DROP

# Allow management access only from trusted internal subnet
iptables -A INPUT -s 192.168.1.0/24 -p tcp --dport 80 -j ACCEPT