CVE-2026-71910: DrayTek VigorAP Command Injection RCE Flaw

CVE-2026-71910 Overview

CVE-2026-71910 is an operating system command injection vulnerability affecting multiple DrayTek VigorAP access point models. The flaw resides in the apautotest function of the web management interface. Insufficient validation of the CMD0, CMD3, and CMD6 request fields allows attacker-supplied input to reach a shell execution context. A remote attacker with valid administrative credentials can execute arbitrary commands with root privileges on the underlying device. The vulnerability is classified under CWE-78, OS Command Injection.

Critical Impact
Authenticated remote attackers can achieve root-level command execution on affected VigorAP devices, enabling full device takeover, network pivoting, and persistent implants in the wireless access layer.

Affected Products

Multiple DrayTek VigorAP series access point models (refer to the DrayTek advisory for the model list)
Firmware versions prior to the August 2026 security release
Devices exposing the web management interface to reachable networks

Discovery Timeline

2026-08-24 - CVE-2026-71910 published to NVD
2026-08-26 - Last updated in NVD database

Technical Details for CVE-2026-71910

Vulnerability Analysis

The defect lives in the apautotest handler exposed by the VigorAP web administration interface. The handler accepts several parameters used to trigger automated test commands, including CMD0, CMD3, and CMD6. These parameter values are passed into a shell execution routine without adequate sanitization or argument separation. An attacker who supplies shell metacharacters within any of these fields breaks out of the intended command context and appends arbitrary operating system commands. Because the web management daemon runs as root on VigorAP firmware, injected commands inherit root privileges. Exploitation requires valid administrator credentials, which limits opportunistic abuse but does not prevent attacks using default credentials, phished sessions, or credentials harvested from prior compromise.

Root Cause

The root cause is missing input validation on the CMD0, CMD3, and CMD6 fields before those values are concatenated into a command string executed by a shell. The handler trusts operator-supplied input rather than treating it as untrusted data. Neutralizing shell metacharacters, using an allowlist of legitimate test values, or invoking the target binary with an argument array rather than a shell would have prevented the injection.

Attack Vector

The attack path is network-based against the VigorAP web management interface. An authenticated administrator session sends a crafted HTTP request to the apautotest endpoint with a payload embedded in CMD0, CMD3, or CMD6. Injected shell operators such as command separators, subshells, or backticks route execution to attacker-chosen binaries. The resulting root shell can be used to modify firmware, add persistence, capture wireless traffic, or pivot into internal networks. See the VulnCheck DrayTek Advisory for technical details of the vulnerable parameters.

No verified public exploit code is available at the time of publication. The vulnerability is described in prose in the vendor and third-party advisories rather than through a released proof-of-concept.

Detection Methods for CVE-2026-71910

Indicators of Compromise

HTTP POST requests to the apautotest endpoint containing shell metacharacters such as ;, |, &, $(, or backticks inside CMD0, CMD3, or CMD6 parameter values
Unexpected outbound connections originating from VigorAP management IP addresses to attacker-controlled hosts
New or modified files in writable firmware paths, unexpected iptables rule changes, or spawned telnetd, nc, or wget processes on the device

Detection Strategies

Inspect web server and management logs on VigorAP devices for administrator sessions issuing apautotest requests, especially outside normal maintenance windows
Deploy network intrusion detection signatures that flag HTTP requests to the VigorAP management interface containing shell metacharacters in CMD parameters
Correlate administrator authentication events with subsequent configuration changes and firmware access to identify credential misuse

Monitoring Recommendations

Forward VigorAP syslog and authentication events to a centralized logging platform for longitudinal analysis
Monitor management VLANs for anomalous egress from access points, which normally do not initiate outbound connections
Alert on administrative logins from unexpected source addresses or geolocations

How to Mitigate CVE-2026-71910

Immediate Actions Required

Apply the firmware update referenced in the DrayTek Security Advisory to every affected VigorAP model
Rotate administrator credentials on all VigorAP devices and remove any default or shared accounts
Restrict access to the web management interface to a dedicated management network or VPN

Patch Information

DrayTek released fixed firmware for the affected VigorAP series in the August 2026 security advisory covering multiple remote code execution and buffer overflow issues, including the apautotest command injection. Administrators should consult the vendor advisory for the specific fixed firmware version applicable to each model and validate the upgrade in a maintenance window.

Workarounds

Disable remote administration on the WAN interface and permit management only from trusted internal subnets
Enforce strong, unique administrator passwords and enable account lockout to slow credential brute-force attempts
Segment access points onto a dedicated management VLAN with strict ACLs blocking arbitrary outbound traffic from device management IPs

bash

# Configuration example: restrict VigorAP management access at an upstream firewall
# Replace 10.10.20.0/24 with your management network and 192.0.2.10 with the AP address
iptables -A FORWARD -s 10.10.20.0/24 -d 192.0.2.10 -p tcp --dport 443 -j ACCEPT
iptables -A FORWARD -d 192.0.2.10 -p tcp --dport 443 -j DROP
iptables -A FORWARD -d 192.0.2.10 -p tcp --dport 80  -j DROP