CVE-2026-38711: Router Command Injection RCE Vulnerability

CVE-2026-38711 Overview

CVE-2026-38711 is a command injection vulnerability affecting multiple Cudy router models. The flaw resides in the system.upgrade_check interface and allows unauthenticated attackers to execute arbitrary commands as root through crafted input. The vulnerability is tracked under CWE-77 (Improper Neutralization of Special Elements used in a Command).

Affected firmware includes TR1200 v2.4.15, TR3000 v2.4.21, WR300 v2.4.25, WR1200 v2.4.23, WR1300 v2.4.22, WR1500 v2.3.10, WR3000 v2.4.19, WR3600 v2.3.16, and WR6500 v2.3.15. The vulnerability is network-exploitable with low complexity and no authentication requirement.

Critical Impact
Unauthenticated remote attackers can execute arbitrary commands as root, gaining full control over affected Cudy routers.

Affected Products

Cudy TR1200 v2.4.15 and TR3000 v2.4.21
Cudy WR300 v2.4.25, WR1200 v2.4.23, WR1300 v2.4.22, WR1500 v2.3.10
Cudy WR3000 v2.4.19, WR3600 v2.3.16, and WR6500 v2.3.15

Discovery Timeline

2026-07-31 - CVE-2026-38711 published to NVD
2026-08-03 - Last updated in NVD database

Technical Details for CVE-2026-38711

Vulnerability Analysis

The vulnerability is a command injection flaw (CWE-77) in the system.upgrade_check interface exposed by the router firmware. This interface accepts user-supplied input that is passed to an underlying shell or system command without adequate sanitization or neutralization of command metacharacters.

Because the router's management services execute with root privileges, successful injection grants the attacker full control of the underlying Linux system. Attackers can pivot to modify firmware, extract credentials, intercept traffic, or add the device to a botnet.

The EPSS score of 2.619% (83.964 percentile) indicates elevated likelihood of exploitation attempts relative to typical CVEs. No public proof-of-concept exploit is currently listed, and the flaw is not on the CISA Known Exploited Vulnerabilities catalog.

Root Cause

The root cause is missing input validation and improper neutralization of shell metacharacters within the system.upgrade_check handler. Parameters supplied to the upgrade-check routine are concatenated into a system command string before execution, allowing injected operators such as ;, |, &&, or backticks to break out of the intended command context.

Attack Vector

An attacker sends a crafted HTTP request to the router's management interface targeting the system.upgrade_check endpoint. The malicious payload contains shell metacharacters that append attacker-controlled commands to the intended upgrade-check invocation. The injected commands run in the security context of the web management service, which operates as root on affected Cudy firmware.

Exploitation requires network reachability to the router's management interface. When management access is exposed to the WAN, attackers can exploit the flaw from the internet without prior credentials.

Refer to the Cudy Security Advisory SA-26-7-7-KJW-1-B for vendor-provided technical detail.

Detection Methods for CVE-2026-38711

Indicators of Compromise

Unexpected outbound connections initiated by the router to unfamiliar IP addresses, particularly on non-standard ports.
HTTP requests to router management endpoints containing shell metacharacters (;, |, &, backticks, $() in upgrade_check parameters.
New or modified processes, cron entries, or startup scripts on the router that were not deployed by the administrator.
DNS queries from the router to domains associated with known botnets or malware infrastructure.

Detection Strategies

Inspect router web-management access logs for POST or GET requests targeting system.upgrade_check with anomalous parameter content.
Deploy network-based intrusion detection signatures that flag command-injection payloads directed at Cudy management endpoints.
Baseline outbound traffic from network infrastructure devices and alert on deviations such as connections to previously unseen hosts.

Monitoring Recommendations

Forward router syslog and management-plane telemetry to a centralized SIEM for correlation with endpoint and network events.
Monitor for firmware version changes and unauthorized configuration modifications on Cudy devices.
Alert on any exposure of router administrative interfaces to the WAN through periodic external attack-surface scans.

How to Mitigate CVE-2026-38711

Immediate Actions Required

Restrict access to the router's management interface to trusted LAN segments and disable WAN-side administrative access.
Apply the firmware update referenced in the Cudy Security Advisory SA-26-7-7-KJW-1-B as soon as it is available for your model.
Audit affected devices for signs of prior compromise, including unauthorized configuration changes and unknown processes.

Patch Information

Cudy has published advisory SA-26-7-7-KJW-1-B covering the affected firmware versions. Administrators should consult the vendor advisory for the specific fixed firmware version corresponding to each router model and apply the update through the device management console.

Workarounds

Block inbound access to the router management interface from untrusted networks using upstream firewall rules or ISP-provided controls.
Place vulnerable routers behind a segmentation boundary and disable remote management features (HTTP, HTTPS, Telnet, SSH) on the WAN interface until patched.
If management access must remain available, restrict it by source IP allowlist and enforce strong administrative credentials.

bash

# Example: restrict router management interface to a trusted LAN subnet using an upstream firewall
iptables -A FORWARD -p tcp -d <router_ip> --dport 80  -s 192.168.10.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -s 192.168.10.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 80  -j DROP
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -j DROP