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Command InjectionWeakness · CWE-77

CVE-2026-6140

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 vulnerability was found in Totolink A7100RU 7.4cu.2313_b20191024. This impacts the function UploadFirmwareFile of the file /cgi-bin/cstecgi.cgi of the component CGI Handler. Performing a manipulation of the argument FileName results in os command injection. The attack may be initiated remotely. The exploit has been made public and could 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's CGI handler (/cgi-bin/cstecgi.cgi). The UploadFirmwareFile function improperly handles the FileName parameter, allowing remote attackers to inject and execute arbitrary OS commands. The CVSS 9.8 score reflects the critical severity of unauthenticated remote command execution.

MitigationPrimary mitigation is applying vendor firmware patch when available. Until then, disable remote management interfaces, restrict access via firewall/network segmentation, and monitor for exploitation attempts. The public exploit increases urgency for organizations with exposed devices.

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. Confirm device model is Totolink A7100RU
    Access the router web interface or check the device label, or query the device's HTTP headers or management page for the exact model identifier
    Affected if The device is a Totolink A7100RU router - this is the only affected model listed in the CVE
  2. Verify CGI endpoint is externally accessible
    Attempt to reach http://<device-ip>/cgi-bin/cstecgi.cgi from a network location. A successful HTTP 200 or similar response indicates the CGI handler is reachable
    Affected if The /cgi-bin/cstecgi.cgi endpoint responds to requests - this is the attack surface for the vulnerability
  3. Check current firmware version
    Log into the router admin interface and look for a firmware version field (usually under Status, System, or About pages), or query the device via SNMP or telnet if available
    Affected if The installed firmware version differs from the patched version - compare against vendor release notes when available to determine if the fix is applied
  4. Determine if remote management is enabled
    In the router web interface, locate the remote management or admin access settings (often under Advanced, Administration, or Security). Check if HTTP/HTTPS admin access is permitted from WAN/external IPs
    Affected if Remote administration or the CGI handler is accessible from WAN/outside the local network - the vulnerability is remotely exploitable when the interface is exposed
  5. Inspect for indicators of compromise
    Review router system logs for suspicious commands, unexpected processes, or unauthorized configuration changes. Check for new admin accounts, port forwards, or unusual DNS settings
    Affected if Log entries show execution of unknown commands, unexpected file uploads, or the CGI endpoint receiving unusual FileName parameter values - these suggest active exploitation

A Totolink A7100RU device with externally accessible /cgi-bin/cstecgi.cgi endpoint and an unpatched firmware version is affected and at risk of unauthenticated remote command injection.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Primary mitigation is applying vendor firmware patch when available. Until then, disable remote management interfaces, restrict access via firewall/network segmentation, and monitor for exploitation attempts. The public exploit increases urgency for organizations with exposed devices.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2026-6140 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
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