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Command InjectionWeakness · CWE-77

CVE-2026-6138

CRITICAL · 9.8 CVSS v3.1 Published 2026-04-13
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A flaw has been found in Totolink A7100RU 7.4cu.2313_b20191024. The impacted element is the function setAccessDeviceCfg of the file /cgi-bin/cstecgi.cgi of the component CGI Handler. This manipulation of the argument mac causes os command injection. The attack can be initiated remotely. The exploit has been published and may be used.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

OS command injection vulnerability in Totolink A7100RU router firmware 7.4cu.2313_b20191024. The setAccessDeviceCfg function in /cgi-bin/cstecgi.cgi does not properly sanitize the 'mac' parameter before passing it to system shell commands, allowing remote attackers to execute arbitrary OS commands.

MitigationApply vendor firmware update when available; until then, restrict network access to the CGI interface via firewall rules or disable remote management access entirely.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify device model and firmware version
    Log into the Totolink router web interface (usually at 192.168.0.1 or 192.168.1.1) and navigate to System Status or Firmware Upgrade page to confirm the device is an A7100RU and note the firmware version displayed.
    Affected if The device model shows A7100RU and firmware version matches 7.4cu.2313_b20191024 or is an earlier version from the same release cycle.
  2. Verify vulnerable CGI binary exists
    Attempt to access the CGI binary via HTTP GET or POST request to /cgi-bin/cstecgi.cgi on the router's IP address. This may return an error or a response indicating the binary exists.
    Affected if The /cgi-bin/cstecgi.cgi endpoint is reachable and responds to requests.
  3. Confirm remote management is enabled
    In the router web interface, check the remote management settings (usually under Advanced Settings, Administration, or Access Control). Look for options like 'Remote Management', 'Web Management from WAN', or 'Enable External Web Interface' and confirm they are enabled.
    Affected if Remote management access to the web interface is enabled, allowing the vulnerable CGI to be reached from external IP addresses.
  4. Check for command injection vulnerability in mac parameter
    If you have authorized access, send a crafted HTTP POST request to /cgi-bin/cstecgi.cgi with action set to 'setAccessDeviceCfg' and the 'mac' parameter containing a test payload (e.g., `; echo vulnerable #`). Observe if command output is reflected in the response.
    Affected if The 'mac' parameter in the setAccessDeviceCfg function executes shell commands without proper sanitization.

If the device is a Totolink A7100RU running firmware 7.4cu.2313_b20191024 (or earlier) with the /cgi-bin/cstecgi.cgi interface accessible remotely, the device is vulnerable to OS command injection via the unsanitized 'mac' parameter.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply vendor firmware update when available; until then, restrict network access to the CGI interface via firewall rules or disable remote management access entirely.

Recommended fix Moderate confidence
  1. Identify the vulnerable CGI endpoint /cgi-bin/cstecgi.cgi and the setAccessDeviceCfg function that processes the 'mac' parameter.
  2. Apply a firewall rule or ACL to block external (Internet) traffic from reaching the /cgi-bin/cstecgi.cgi endpoint (e.g., iptables -A INPUT -p tcp --dport 80 -s <trusted_net> -j ACCEPT; iptables -A INPUT -p tcp --dport 80 -j DROP).
  3. If the device's web UI is not required for external management, disable remote HTTP/HTTPS access entirely or limit it to trusted IP addresses only.
  4. Alternatively, disable the CGI handler in the web server configuration if the functionality is not needed, or remove the cstecgi.cgi binary from the device.
  5. Monitor logs for any attempts to exploit the 'mac' parameter and consider deploying an intrusion detection system (IDS) to alert on suspicious requests.

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
11.0 hours of engineering $2,000
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-6138 in production — separate from our analysis above.

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