CVE-2026-5995 Overview
CVE-2026-5995 is an operating system (OS) command injection vulnerability affecting the Totolink A7100RU router running firmware version 7.4cu.2313_b20191024. The flaw resides in the setMiniuiHomeInfoShow function within the /cgi-bin/cstecgi.cgi binary, which is part of the device's CGI Handler component. Attackers can manipulate the lan_info argument to inject arbitrary operating system commands. The vulnerability is exploitable remotely over the network without authentication or user interaction. A public exploit is available, increasing the likelihood of opportunistic attacks against exposed devices.
Critical Impact
Unauthenticated remote attackers can execute arbitrary OS commands on the router with the privileges of the CGI process, leading to full device compromise.
Affected Products
- Totolink A7100RU router
- Firmware version 7.4cu.2313_b20191024
- /cgi-bin/cstecgi.cgi CGI Handler component
Discovery Timeline
- 2026-04-10 - CVE-2026-5995 published to NVD
- 2026-04-27 - Last updated in NVD database
Technical Details for CVE-2026-5995
Vulnerability Analysis
The vulnerability is classified under [CWE-77] Improper Neutralization of Special Elements used in a Command. The setMiniuiHomeInfoShow handler in /cgi-bin/cstecgi.cgi accepts a lan_info parameter from HTTP requests and passes its contents to an operating system command interpreter without proper sanitization. Attackers who append shell metacharacters such as ;, |, or backticks to the lan_info value can break out of the intended command context and execute arbitrary binaries. Because the CGI process typically runs with elevated privileges on consumer routers, successful exploitation results in complete control over the device, including network traffic interception, DNS hijacking, and persistent backdoor installation.
Root Cause
The root cause is the lack of input validation and command argument sanitization within the setMiniuiHomeInfoShow function. User-supplied data from the lan_info field is concatenated directly into a shell command string before invocation, allowing injected metacharacters to be interpreted by the shell.
Attack Vector
Exploitation requires only network reachability to the router's web management interface. An attacker sends a crafted HTTP POST request to /cgi-bin/cstecgi.cgi invoking the setMiniuiHomeInfoShow topic with a malicious lan_info value containing command separators followed by arbitrary commands. The attack requires no credentials or user interaction. Public exploit material is available through the GitHub Vulnerability Repository and VulDB entry 356549, which describe the request structure used to trigger the command injection.
Detection Methods for CVE-2026-5995
Indicators of Compromise
- HTTP POST requests to /cgi-bin/cstecgi.cgi containing the setMiniuiHomeInfoShow topic with shell metacharacters such as ;, |, &, or backticks in the lan_info parameter.
- Unexpected outbound network connections originating from the router to attacker-controlled infrastructure.
- Unusual processes, modified DNS settings, or new iptables rules on the device console.
Detection Strategies
- Inspect web server and reverse proxy logs for requests targeting cstecgi.cgi with non-printable or shell-control characters in POST bodies.
- Deploy network intrusion detection signatures that match the setMiniuiHomeInfoShow function name combined with command injection patterns in HTTP traffic.
- Compare router firmware checksums and configuration files against known-good baselines to identify tampering.
Monitoring Recommendations
- Continuously monitor egress traffic from network infrastructure devices for anomalous destinations, ports, or volumes.
- Alert on management interface access from untrusted networks or non-administrative source addresses.
- Forward router syslog data to a centralized log platform and create alerts on authentication failures, CGI errors, and configuration changes.
How to Mitigate CVE-2026-5995
Immediate Actions Required
- Restrict access to the router's web management interface so it is reachable only from trusted internal management subnets.
- Disable remote WAN-side administration on the Totolink A7100RU until a fixed firmware version is available.
- Audit affected devices for signs of compromise, including unauthorized configuration changes and unknown processes.
Patch Information
No vendor patch has been published at the time of disclosure. Refer to the Totolink Security Page for firmware updates and advisories. Detailed vulnerability tracking is available at VulDB #356549 and the corresponding VulDB CTI record.
Workarounds
- Place the affected router behind an upstream firewall and block inbound HTTP and HTTPS access to the management interface from untrusted networks.
- Segment the router from sensitive internal assets to limit lateral movement should the device be compromised.
- Replace the affected hardware with a supported model if the vendor does not release a timely firmware fix.
# Example: Block external access to the router management interface using iptables on an upstream gateway
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -i <wan_iface> -j DROP
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -i <wan_iface> -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
