CVE-2025-4453: D-Link DIR-619L RCE Vulnerability

CVE-2025-4453 Overview

A critical command injection vulnerability has been discovered in the D-Link DIR-619L wireless router firmware version 2.04B04. The vulnerability resides in the formSysCmd function, where improper handling of the sysCmd argument allows remote attackers to inject and execute arbitrary system commands on the affected device. This vulnerability is particularly concerning as it affects a product that has reached end-of-life status and is no longer supported by D-Link.

Critical Impact

Remote attackers with low-level privileges can exploit this command injection vulnerability to execute arbitrary commands on the router, potentially gaining full control of the device and using it as a pivot point for further network attacks.

Affected Products

• D-Link DIR-619L Firmware version 2.04B04
• D-Link DIR-619L Hardware (End-of-Life Product)

Discovery Timeline

• May 9, 2025 - CVE-2025-4453 published to NVD
• May 13, 2025 - Last updated in NVD database

Technical Details for CVE-2025-4453

Vulnerability Analysis

This command injection vulnerability (CWE-77) occurs within the formSysCmd function of the D-Link DIR-619L router firmware. The function fails to properly sanitize user-supplied input passed through the sysCmd parameter before incorporating it into system-level command execution. This allows an attacker to craft malicious requests that include shell metacharacters or additional commands, which are then executed with the privileges of the web server process running on the router.

The vulnerability is classified under CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component) and CWE-77 (Improper Neutralization of Special Elements used in a Command), indicating a fundamental failure in input validation and command construction.

Root Cause

The root cause of this vulnerability lies in the insufficient input validation within the formSysCmd function. The sysCmd argument is passed directly to system command execution routines without proper sanitization or escaping of shell metacharacters. This design flaw allows attackers to break out of the intended command context and inject arbitrary commands using common shell operators such as semicolons (;), pipes (|), or command substitution characters.

Attack Vector

The attack can be initiated remotely over the network. An attacker with low-level privileges on the router's web interface can manipulate the sysCmd parameter in HTTP requests to the formSysCmd endpoint. By injecting shell commands into this parameter, the attacker can execute arbitrary code on the underlying Linux-based operating system of the router.

The exploitation requires network access to the router's administrative interface, which may be accessible from the local network or, in misconfigured setups, from the internet. Successful exploitation does not require user interaction, making this vulnerability particularly dangerous for unattended devices.

A proof-of-concept demonstrating this vulnerability is available in the GitHub PoC Repository. Administrators should review this documentation to understand the attack mechanics and validate their exposure.

Detection Methods for CVE-2025-4453

Indicators of Compromise

• Unusual outbound network connections from the router to unknown external IP addresses
• Modified system files or configuration changes on the router
• Unexpected processes running on the device observable through diagnostic interfaces
• Authentication logs showing repeated access to the formSysCmd endpoint

Detection Strategies

• Monitor HTTP access logs for requests to the formSysCmd endpoint containing suspicious characters such as ;, |, &, or backticks
• Implement network intrusion detection rules to identify command injection patterns in router web traffic
• Deploy network traffic analysis to detect anomalous behavior from router IP addresses
• Use SentinelOne Singularity for network visibility to identify compromised IoT devices exhibiting suspicious communication patterns

Monitoring Recommendations

• Enable logging on all D-Link DIR-619L devices if available and centralize log collection
• Monitor for firmware modification attempts or unusual administrative access patterns
• Implement network segmentation to isolate legacy and end-of-life network devices
• Regularly audit devices on the network for end-of-life firmware that may contain unpatched vulnerabilities

How to Mitigate CVE-2025-4453

Immediate Actions Required

• Replace the D-Link DIR-619L router with a currently supported device, as this product is end-of-life
• Disable remote administration if the device must remain temporarily in use
• Restrict access to the router's administrative interface to trusted IP addresses only
• Implement network segmentation to isolate the vulnerable device from critical network resources

Patch Information

D-Link has indicated that this vulnerability affects a product that is no longer supported by the maintainer. As an end-of-life device, no security patches will be released for the DIR-619L firmware version 2.04B04. The vendor was contacted early about this disclosure but due to the product's end-of-life status, remediation through official patches is not available. For additional information, visit the D-Link Official Website.

Workarounds

• Replace the affected router with a currently supported model that receives security updates
• If immediate replacement is not possible, disable the web-based administrative interface entirely
• Configure firewall rules to block external access to the router's management ports
• Use a VPN or other secure access method if remote administration is absolutely required

# Example: Restrict administrative access via iptables on upstream firewall
# Block external access to router management interface
iptables -A FORWARD -d 192.168.0.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.0.1 -p tcp --dport 443 -j DROP

# Allow only specific trusted IP for management
iptables -I FORWARD -s 192.168.0.100 -d 192.168.0.1 -p tcp --dport 80 -j ACCEPT