CVE-2026-71925 Overview
CVE-2026-71925 is an OS command injection vulnerability [CWE-78] affecting multiple DrayTek VigorSwitch models. The flaw resides in the getDetail function of the device's web management interface. Insufficient filtering of the username and password fields allows attackers to inject shell metacharacters that reach the underlying command interpreter. A remote authenticated attacker with administrative credentials can execute arbitrary commands with root privileges on the switch. Successful exploitation grants full control of the affected network device, including the ability to pivot into adjacent network segments.
Critical Impact
Authenticated attackers can achieve root-level remote code execution on DrayTek VigorSwitch devices, compromising confidentiality, integrity, and availability of the switch and connected network traffic.
Affected Products
- Multiple DrayTek VigorSwitch series models (see vendor advisory for specific model list)
- Firmware versions prior to the August 2026 security update
- Devices exposing the web management interface
Discovery Timeline
- 2026-08-24 - CVE-2026-71925 published to NVD
- 2026-08-26 - Last updated in NVD database
Technical Details for CVE-2026-71925
Vulnerability Analysis
The vulnerability exists in the getDetail function exposed through the VigorSwitch web management interface. The function accepts username and password fields but fails to sanitize shell metacharacters before passing them to a system command execution routine. Attackers with valid administrative credentials submit crafted input containing shell operators such as semicolons, backticks, or command substitution sequences. The injected commands execute in the context of the web server process, which runs as root on affected DrayTek switches. Compromised switches enable traffic interception, credential harvesting, VLAN hopping, and lateral movement into adjacent network segments.
Root Cause
The root cause is missing input validation and improper neutralization of special elements used in an OS command [CWE-78]. The getDetail function concatenates user-supplied authentication fields directly into a shell command string without escaping or allowlisting. Refer to the VulnCheck DrayTek Advisory for the technical breakdown.
Attack Vector
Exploitation requires network access to the switch web interface and valid administrative credentials. An attacker sends an HTTP request to the getDetail endpoint with shell metacharacters embedded in the username or password parameter. The device executes the injected command with root privileges and returns control output through the standard response channel. Credentials obtained through phishing, brute force, default credential reuse, or prior compromise satisfy the privilege requirement.
No verified proof-of-concept code is publicly available. See the DrayTek Security Advisory for vendor guidance.
Detection Methods for CVE-2026-71925
Indicators of Compromise
- HTTP requests to the VigorSwitch management interface containing shell metacharacters (;, |, `, $()) within username or password parameters
- Unexpected child processes spawned by the switch web server process
- Outbound connections from the switch to unknown external hosts, indicating reverse shell or data exfiltration
- Unauthorized configuration changes or new administrative accounts on the device
Detection Strategies
- Inspect web server access logs on the switch for requests to the getDetail endpoint containing suspicious characters in authentication fields
- Deploy network intrusion detection rules that flag command injection patterns targeting DrayTek management URLs
- Monitor for anomalous SNMP, syslog, or configuration changes originating from VigorSwitch devices
- Correlate switch management interface access with authorized administrator activity windows
Monitoring Recommendations
- Forward switch syslog and web access logs to a centralized SIEM for retention and correlation
- Alert on any command injection signature match targeting network infrastructure IP ranges
- Track authentication events to VigorSwitch management interfaces and investigate logins from unexpected source addresses
How to Mitigate CVE-2026-71925
Immediate Actions Required
- Apply the August 2026 firmware update from DrayTek to all affected VigorSwitch models
- Restrict access to the switch web management interface to a dedicated management VLAN or jump host
- Rotate all administrative credentials on affected switches and eliminate any shared or default passwords
- Audit switch configurations and account lists for unauthorized changes indicating prior exploitation
Patch Information
DrayTek released firmware updates addressing the getDetail command injection in August 2026. Consult the DrayTek Security Advisory for the specific fixed firmware version applicable to each VigorSwitch model.
Workarounds
- Disable remote access to the web management interface and restrict management to a physically isolated network
- Enforce access control lists on the switch that permit management connections only from authorized administrator workstations
- Require multi-factor authentication on jump hosts used to reach the switch management plane
- Monitor and rate-limit access to the getDetail endpoint at an upstream firewall or reverse proxy
# Example ACL restricting VigorSwitch management access to a management subnet
# Replace 10.10.99.0/24 with your management network and 192.0.2.10 with the switch IP
iptables -A FORWARD -p tcp -d 192.0.2.10 --dport 443 -s 10.10.99.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d 192.0.2.10 --dport 443 -j DROP
iptables -A FORWARD -p tcp -d 192.0.2.10 --dport 80 -s 10.10.99.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d 192.0.2.10 --dport 80 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
