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CVE-2026-71921 – Pre-Authentication Command Injection (RCE) – DrayTek VigorSwitch Series

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Summary

CVE-2026-71921 is a critical, pre-authentication OS command injection vulnerability affecting multiple models in the DrayTek VigorSwitch product line. The flaw resides in the setget.cgi web management interface and allows a remote, unauthenticated attacker to execute arbitrary commands with root privileges on the device. The issue carries a CVSS v3.1 base score of 9.8 (Critical) and a CVSS v4.0 score of 9.3 (Critical), reflecting network-based exploitability with no authentication or user interaction required.

Technical details

  • Root cause: Insufficient filtering/sanitization of the pass field submitted to the setget.cgi interface before it is passed to a system command execution routine (CWE-78, OS Command Injection).
  • Trigger conditions: An attacker sends a specially crafted request containing shell metacharacters in the pass field to the exposed setget.cgi endpoint; no valid credentials or prior session are required.
  • Attack vector: Network (remote), Attack Complexity: Low, Privileges Required: None, User Interaction: None — consistent with pre-authentication exploitation over the management interface.
  • Impact: Successful exploitation grants the attacker arbitrary command execution with root-level privileges on the switch, resulting in full compromise of confidentiality, integrity, and availability of the device and any network segments it manages.

Affected software

DrayTek VigorSwitch models with firmware prior to the fixed versions listed below:

  • VigorSwitch G2540xs, P2540xs, FX2120 — versions before 3.9.10
  • VigorSwitch G2282x, P2282x — versions before 2.10.6
  • VigorSwitch Q2300x, PQ2300xb — versions before 2.10.7
  • VigorSwitch G2542x, P2542x, P2542xh — versions before 3.10.6
  • VigorSwitch PX2060, G1280, P1280, P1281x, G1282, P1282, G2121, P2121, PQ2121x, Q2121x, G2280x, P2280x, Q2200x, PQ2200xb, G2100, P2100, G2540x, P2540x — versions before 2.9.10

Severity

  • CVSS v3.1: 9.8 (Critical) — AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  • CVSS v4.0: 9.3 (Critical) — CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Mitigation and recommended actions

  • Immediate: Upgrade affected VigorSwitch devices to the fixed firmware versions corresponding to each model, as listed above (3.9.10, 2.10.6, 2.10.7, 3.10.6, or 2.9.10 depending on model).
  • If immediate patching is not possible:
    • Restrict access to the switch management interface (setget.cgi and other web-admin paths) to trusted internal management networks only; do not expose it to the public internet.
    • Place management interfaces behind a VPN or dedicated out-of-band management network.
    • Use firewall/ACL rules to limit inbound access to the device’s management ports to known administrative IP addresses.
    • Monitor device logs and network traffic for anomalous or malformed requests to the CGI management interface.

References

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