CVE-2026-4195 Overview
A command injection vulnerability has been identified in multiple D-Link Network Attached Storage (NAS) devices affecting the /cgi-bin/wizard_mgr.cgi file. This flaw allows remote attackers with low privileges to execute arbitrary commands on vulnerable devices by manipulating input parameters passed to the CGI script. The vulnerability impacts a wide range of D-Link DNS and DNR series NAS devices with firmware versions up to 20260205.
Critical Impact
Remote attackers can exploit this command injection vulnerability to execute arbitrary system commands on affected D-Link NAS devices, potentially leading to complete device compromise, data theft, or use of the device in botnet operations.
Affected Products
- D-Link DNS-120, DNS-315L, DNS-320, DNS-320L, DNS-320LW Firmware
- D-Link DNS-321, DNS-323, DNS-325, DNS-326, DNS-327L Firmware
- D-Link DNS-340L, DNS-343, DNS-345, DNS-726-4 Firmware
- D-Link DNS-1100-4, DNS-1200-05, DNS-1550-04 Firmware
- D-Link DNR-202L, DNR-322L, DNR-326 Firmware
Discovery Timeline
- March 16, 2026 - CVE-2026-4195 published to NVD
- March 19, 2026 - Last updated in NVD database
Technical Details for CVE-2026-4195
Vulnerability Analysis
This vulnerability is a command injection flaw (CWE-77) with an underlying injection weakness (CWE-74) in the D-Link NAS web management interface. The affected CGI script wizard_mgr.cgi fails to properly sanitize user-supplied input before passing it to system commands. When an authenticated attacker sends specially crafted requests to this endpoint, the malicious input is interpreted as shell commands and executed with the privileges of the web server process.
The attack requires network access and low-level authentication, making it exploitable by any user with valid credentials to the device's web interface. Many D-Link NAS devices in consumer and small business environments use default or weak credentials, significantly increasing the practical exploitability of this vulnerability. The exploit has been publicly disclosed and may be actively used in the wild.
Root Cause
The root cause of this vulnerability lies in improper input validation and sanitization within the wizard_mgr.cgi script. The CGI handler constructs system commands using user-controlled input without proper escaping or validation. This allows shell metacharacters and command separators to be injected, enabling arbitrary command execution. The lack of input sanitization is a common issue in legacy embedded device firmware where security was not prioritized during development.
Attack Vector
The attack is executed remotely over the network through HTTP requests to the vulnerable CGI endpoint. An attacker with valid authentication credentials can craft malicious HTTP requests containing shell metacharacters in parameters processed by wizard_mgr.cgi. When the CGI script processes these parameters, the injected commands are executed on the underlying Linux operating system.
A typical attack flow involves:
- Authenticating to the D-Link NAS web interface
- Sending a crafted HTTP request to /cgi-bin/wizard_mgr.cgi with command injection payloads
- The injected commands execute with web server privileges
- Attackers can establish persistence, exfiltrate data, or pivot to other network resources
For detailed technical information about the exploitation mechanism, refer to the GitHub vulnerability documentation.
Detection Methods for CVE-2026-4195
Indicators of Compromise
- Unusual HTTP requests to /cgi-bin/wizard_mgr.cgi containing shell metacharacters such as ;, |, &, or backticks
- Unexpected outbound network connections from D-Link NAS devices to external IP addresses
- Creation of unauthorized user accounts or SSH keys on the NAS device
- Anomalous process execution originating from the web server process
Detection Strategies
- Monitor web server access logs for requests to wizard_mgr.cgi with suspicious parameter values containing command injection patterns
- Deploy network intrusion detection signatures to identify HTTP requests with shell metacharacters targeting D-Link NAS CGI endpoints
- Implement behavioral analysis to detect unexpected command execution or shell spawning from web server processes on NAS devices
Monitoring Recommendations
- Enable and centralize logging from D-Link NAS devices to a SIEM platform for correlation and alerting
- Configure network monitoring to alert on outbound connections from NAS devices to non-standard ports or unknown destinations
- Regularly audit running processes on NAS devices to identify unauthorized or suspicious activity
How to Mitigate CVE-2026-4195
Immediate Actions Required
- Identify all D-Link DNS and DNR series NAS devices on the network and determine their firmware versions
- Restrict network access to the web management interface using firewall rules, limiting access to trusted administrator IP addresses only
- Change default credentials and enforce strong passwords for all user accounts on affected devices
- Consider isolating affected NAS devices on a separate network segment with strict access controls
Patch Information
As many of the affected D-Link NAS models have reached end-of-life status, official firmware patches may not be available. Check the D-Link official website for any security advisories or firmware updates for your specific model. For end-of-life devices, D-Link recommends device replacement with actively supported models.
Additional technical details and vulnerability information can be found at VulDB #351107.
Workarounds
- Disable remote administration access to the NAS device entirely if not required for operations
- Implement network-level access controls using firewall rules to restrict access to the web management interface
- Deploy a VPN solution and require VPN connectivity for any remote management access to NAS devices
- Monitor and log all access attempts to the device management interface for security auditing
# Example firewall rule to restrict NAS web interface access
# Replace NAS_IP with your device IP and ADMIN_IP with trusted admin IP
iptables -A INPUT -d NAS_IP -p tcp --dport 80 -s ADMIN_IP -j ACCEPT
iptables -A INPUT -d NAS_IP -p tcp --dport 80 -j DROP
iptables -A INPUT -d NAS_IP -p tcp --dport 443 -s ADMIN_IP -j ACCEPT
iptables -A INPUT -d NAS_IP -p tcp --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
