CVE-2026-71924 Overview
CVE-2026-71924 is a command injection vulnerability affecting multiple DrayTek VigorSwitch models. The flaw resides in the getVid function of the device's web management interface. Insufficient filtering of the username and password fields allows attacker-supplied input to reach a command execution context. A remote attacker with valid administrative credentials can execute arbitrary operating system commands with root privileges. The weakness is categorized as [CWE-78] Improper Neutralization of Special Elements used in an OS Command.
Critical Impact
Authenticated attackers can achieve root-level command execution on affected DrayTek VigorSwitch devices, enabling full compromise of switch configuration, traffic, and downstream network segments.
Affected Products
- DrayTek VigorSwitch series (multiple models, refer to vendor advisory)
- Web management interface component exposing the getVid function
- Firmware versions listed in the DrayTek August 2026 advisory
Discovery Timeline
- 2026-08-24 - CVE-2026-71924 published to the National Vulnerability Database (NVD)
- 2026-08-26 - Last updated in NVD database
Technical Details for CVE-2026-71924
Vulnerability Analysis
The vulnerability exists in the getVid function within the DrayTek VigorSwitch web management interface. The function processes the username and password fields submitted during authentication-related workflows. These fields are passed into a command execution context without adequate neutralization of shell metacharacters. An authenticated administrator can inject shell operators such as backticks, semicolons, or command substitution sequences into these fields. The resulting payload executes as root, the privilege level under which the switch's management processes run. Successful exploitation yields arbitrary command execution, persistence opportunities, and pivot capability into adjacent network segments.
Root Cause
The root cause is improper input validation and missing output encoding before shell invocation, aligning with [CWE-78]. The getVid handler concatenates user-controlled username and password values into a command string that is dispatched to a shell interpreter. No allowlist, escaping routine, or safe API such as execve with argument arrays separates data from control characters.
Attack Vector
Exploitation requires network reachability to the VigorSwitch web management interface and valid administrative credentials. The attacker submits a crafted request that embeds shell metacharacters within the username or password parameter consumed by getVid. The injected commands execute with root privileges on the underlying operating system. According to the Exploit Prediction Scoring System (EPSS) data associated with this CVE, the exploitation probability sits in the 86th percentile, indicating elevated interest relative to the broader CVE population.
No verified public exploit code is available at the time of writing. Refer to the VulnCheck DrayTek Advisory for technical details.
Detection Methods for CVE-2026-71924
Indicators of Compromise
- Unexpected shell processes spawned by the switch's web server process during or immediately after authentication requests
- HTTP POST requests to the management interface containing shell metacharacters (;, |, `, $() in username or password fields
- Outbound connections from the switch management IP to attacker-controlled infrastructure
- New or modified system accounts, cron entries, or startup scripts on the switch
Detection Strategies
- Inspect web server and authentication logs for malformed username or password values containing shell control characters targeting the getVid endpoint
- Monitor administrative login events followed by anomalous configuration changes or firmware behavior
- Deploy network intrusion detection signatures that flag command injection patterns in HTTP traffic destined for VigorSwitch management ports
Monitoring Recommendations
- Forward switch syslog and web management logs to a centralized SIEM for correlation with authentication and network telemetry
- Alert on any administrative session originating from unexpected source networks or outside change windows
- Track outbound traffic from management VLANs to detect post-exploitation command-and-control activity
How to Mitigate CVE-2026-71924
Immediate Actions Required
- Apply the firmware updates listed in the DrayTek Security Advisory for each affected VigorSwitch model
- Restrict web management interface access to a dedicated management VLAN and trusted administrator hosts only
- Rotate administrative credentials and enforce strong, unique passwords for every switch
- Audit switch configuration and system accounts for unauthorized modifications
Patch Information
DrayTek published fixed firmware versions in its August 2026 advisory covering the VigorSwitch series. Administrators should identify their model and running firmware, then upgrade to the vendor-specified fixed release. Consult the DrayTek Security Advisory for the authoritative version matrix.
Workarounds
- Disable remote administration on WAN interfaces and permit HTTPS management only from an isolated management subnet
- Enforce access control lists that restrict TCP access to the web management port to specific administrator IP addresses
- Require multi-factor or jump-host based access to any workstation that manages VigorSwitch devices to reduce credential theft risk
# Configuration example: restrict management access to trusted subnet
# (apply via CLI or web UI according to VigorSwitch model documentation)
ip access-list management-acl
permit tcp 10.10.0.0 0.0.0.255 any eq 443
deny tcp any any eq 443
interface vlan 1
ip access-group management-acl in
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
