CVE-2026-1547: Totolink A7000R Firmware RCE Vulnerability

CVE-2026-1547 Overview

CVE-2026-1547 is a command injection vulnerability in the Totolink A7000R router running firmware version 4.1cu.4154. The flaw resides in the setUnloadUserData function of /cgi-bin/cstecgi.cgi, where the plugin_name argument is passed to a shell context without proper sanitization. Attackers can manipulate this parameter to inject operating system commands that the device executes with router privileges. The exploit has been disclosed publicly and the attack is reachable over the network. The vulnerability is classified under [CWE-74] and [CWE-77].

Critical Impact
Authenticated remote attackers can inject arbitrary operating system commands into the router via the plugin_name parameter, leading to unauthorized command execution on the embedded Linux device.

Affected Products

Totolink A7000R hardware device
Totolink A7000R firmware version 4.1cu.4154
Deployments exposing the /cgi-bin/cstecgi.cgi endpoint on accessible network interfaces

Discovery Timeline

2026-01-28 - CVE-2026-1547 published to NVD
2026-04-29 - Last updated in NVD database

Technical Details for CVE-2026-1547

Vulnerability Analysis

The vulnerability is a command injection issue in the setUnloadUserData handler exposed through the Common Gateway Interface (CGI) binary cstecgi.cgi. When the handler processes a request, it consumes the plugin_name parameter from the request body and incorporates it into a system-level command without validating or escaping shell metacharacters. An attacker who can reach the management interface can append additional commands using shell separators such as ;, &&, or backticks. Because the CGI binary runs with elevated privileges on the router, injected commands execute in that same context. The public proof-of-concept demonstrates command execution against the endpoint, lowering the barrier for opportunistic abuse against exposed devices.

Root Cause

The root cause is unsafe handling of user-controlled input within the setUnloadUserData function. The handler passes the plugin_name value directly into a shell invocation, mapping cleanly to [CWE-77] Improper Neutralization of Special Elements used in a Command. No allowlist, escaping, or argument-array execution pattern is applied before the value reaches the command interpreter.

Attack Vector

Exploitation requires network reachability to the router's HTTP service and a valid session context to invoke /cgi-bin/cstecgi.cgi. An attacker crafts a POST request to the CGI endpoint, sets the topicurl to setUnloadUserData, and supplies a plugin_name value containing shell metacharacters followed by the desired commands. The router processes the request and executes the appended commands. A public proof-of-concept is referenced in the GitHub PoC Repository and tracked in VulDB #343231.

No verified exploit code is reproduced here. Refer to the linked advisory for the technical request structure and parameter payload.

Detection Methods for CVE-2026-1547

Indicators of Compromise

HTTP POST requests to /cgi-bin/cstecgi.cgi containing the JSON key topicurl set to setUnloadUserData
Values of plugin_name containing shell metacharacters such as ;, |, &, $(), or backticks
Outbound connections from the router to attacker-controlled infrastructure after suspicious CGI activity
Unexpected processes, cron jobs, or modified startup scripts on the embedded device

Detection Strategies

Inspect web server and reverse proxy logs in front of the router for requests targeting setUnloadUserData with non-alphanumeric plugin_name values
Apply network intrusion detection signatures matching command separators within request bodies sent to cstecgi.cgi
Correlate router administrative endpoint access with subsequent anomalous DNS or outbound TCP traffic originating from the device

Monitoring Recommendations

Restrict management interface exposure and log all access attempts to /cgi-bin/cstecgi.cgi
Forward router syslog, NetFlow, or packet broker data to a central analytics platform for anomaly review
Track firmware versions across the fleet and alert on devices still running 4.1cu.4154

How to Mitigate CVE-2026-1547

Immediate Actions Required

Remove the router's administrative interface from the public internet and limit access to trusted management VLANs
Rotate router administrator credentials and disable any unused remote management features
Audit the device for unauthorized configuration changes, new accounts, persistence scripts, or modified firmware
Inventory all Totolink A7000R deployments running firmware 4.1cu.4154 and prioritize replacement or patching

Patch Information

No vendor-supplied patch URL is published in the available references. Consult the TOTOLink Official Site for firmware updates beyond 4.1cu.4154 and apply any superseding release that addresses the setUnloadUserData handler. Additional advisory context is available at VulDB CTIID #343231.

Workarounds

Block external access to /cgi-bin/cstecgi.cgi at an upstream firewall or perimeter device
Place the router management interface behind a VPN that requires multi-factor authentication
Disable WAN-side HTTP and HTTPS administration in the router configuration until updated firmware is available
Replace end-of-support Totolink A7000R hardware with a supported model if no firmware fix is released

bash

# Configuration example: block external access to the vulnerable CGI endpoint
# Example iptables rule applied on an upstream gateway (adjust interface and router IP)
iptables -I FORWARD -p tcp -d 192.0.2.10 --dport 80 \
  -m string --algo bm --string "/cgi-bin/cstecgi.cgi" -j DROP
iptables -I FORWARD -p tcp -d 192.0.2.10 --dport 443 \
  -m string --algo bm --string "/cgi-bin/cstecgi.cgi" -j DROP