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Command InjectionWeakness · CWE-77

CVE-2026-5853

CRITICAL · 9.8 CVSS v3.1 Published 2026-04-09
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 security vulnerability has been detected in Totolink A7100RU 7.4cu.2313_b20191024. Affected by this vulnerability is the function setIpv6LanCfg of the file /cgi-bin/cstecgi.cgi of the component CGI Handler. Such manipulation of the argument addrPrefixLen leads to os command injection. The attack may be performed from remote. The exploit has been disclosed publicly 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

The Totolink A7100RU router firmware contains an OS command injection vulnerability in the setIpv6LanCfg function of the CGI handler (/cgi-bin/cstecgi.cgi). The addrPrefixLen parameter is not properly sanitized, allowing remote attackers to execute arbitrary OS commands via crafted requests.

MitigationApply vendor-supplied firmware patch when available; in the interim, restrict access to the router's web administration interface using firewall rules or network segmentation to prevent unauthenticated remote exploitation.

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 Totolink A7100RU router model
    Identify the device through the web administration interface, physical label, or network discovery tools (e.g., nmap, router scanning utilities)
    Affected if The device model is Totolink A7100RU
  2. Check firmware version
    Access the router web admin panel, navigate to System or Firmware settings to view the installed version; alternatively, check via telnet/SSH console if available
    Affected if The firmware version has not received the vendor patch for this vulnerability (compare against vendor release notes)
  3. Verify CGI endpoint is reachable
    Attempt an HTTP request to /cgi-bin/cstecgi.cgi on the router's IP address (e.g., curl http://192.168.0.1/cgi-bin/cstecgi.cgi)
    Affected if The CGI handler responds, indicating the web management interface is active
  4. Confirm setIpv6LanCfg function exposure
    The vulnerability exists in the setIpv6LanCfg function - verify the router supports IPv6 LAN configuration through the web interface
    Affected if IPv6 LAN configuration features are available and accessible via the CGI interface
  5. Assess network exposure of admin interface
    Determine if the router web interface is accessible from untrusted networks (WAN side) by checking firewall rules, port forwarding, or performing an external connectivity test
    Affected if The admin interface is exposed to the internet or untrusted network segments

A user is affected if they own a Totolink A7100RU router with an unpatched firmware version and have the web administration interface accessible, enabling remote exploitation via the addrPrefixLen parameter in setIpv6LanCfg.

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-supplied firmware patch when available; in the interim, restrict access to the router's web administration interface using firewall rules or network segmentation to prevent unauthenticated remote exploitation.

Recommended fix Moderate confidence

Latest available firmware version for Totolink A7100RU (contact Totolink support for specific version number)

  1. 1. Visit the official Totolink support website at www.totolink.net and navigate to the downloads/support section for the A7100RU model.
  2. 2. Download the latest available firmware version for the A7100RU router.
  3. 3. Access the router's web administration interface (typically at 192.168.0.1 or 192.168.1.1).
  4. 4. Navigate to the Administration or System settings section and locate the Firmware Upgrade option.
  5. 5. Upload the downloaded firmware file and wait for the upgrade process to complete.
  6. 6. After the router reboots, verify the new firmware version matches the downloaded version.
  7. 7. If no firmware update is available from Totolink, consider replacing the device or implementing network-level filtering to restrict access to the CGI interface (port 80/443) from untrusted networks.
Caveat Firmware upgrades may reset router configuration to defaults; backup current settings before upgrading

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

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,690
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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-2026-5853 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
  • No spam, self-promotion, credentials, or personal data