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Dir 816 FirmwareOperating system · Dlink

CVE-2026-4181

CRITICAL · 9.8 CVSS v3.1 Published 2026-03-16
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
Public exploit 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 flaw has been discovered in D-Link DIR-816 1.10CNB05. This affects an unknown function of the file /goform/form2RepeaterStep2.cgi of the component goahead. The manipulation of the argument key1/key2/key3/key4/pskValue results in stack-based buffer overflow. The attack may be launched remotely. The exploit has been released to the public and may be used for attacks. This vulnerability only affects products that are no longer supported by the maintainer.

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

Stack-based buffer overflow in D-Link DIR-816 1.10CNB05 web CGI component (form2RepeaterStep2.cgi) allows remote attackers to overwrite stack memory via overly long key1/key2/key3/key4/pskValue parameters, potentially enabling arbitrary code execution. The vulnerability affects the goahead web server component handling wireless repeater configuration.

MitigationReplace the end-of-life D-Link DIR-816 device with a currently supported router, as no vendor patch will be released. If immediate replacement is infeasible, disable remote management interfaces and restrict network access to the device.

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

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Dir 816 FirmwareOperating system
Affected:= 1.10cnb05

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 D-Link DIR-816
    Access the device web interface or check the device label/marketing to verify the exact model number is DIR-816
    Affected if Device model is not DIR-816, the vulnerability does not apply
  2. Check firmware version is 1.10cnb05
    Log into the router web UI (typically at 192.168.0.1) and navigate to Status or System settings to view the firmware version, or check via CLI if available
    Affected if Firmware version is not exactly 1.10cnb05, the specific vulnerability does not apply (different versions may have separate issues)
  3. Verify goahead web server is accessible
    Attempt to access the router web interface on ports 80 or 443. The vulnerable form2RepeaterStep2.cgi is part of the goahead web server component
    Affected if Web interface is not accessible or disabled, the attack surface is not present
  4. Check if wireless repeater/repeater configuration is available
    Navigate to the wireless settings section in the router UI and look for repeater, range extender, or WISP configuration options. The vulnerable CGI handles form2RepeaterStep2 parameters
    Affected if The device does not have wireless repeater functionality enabled or accessible, exploitation is not possible through this vector

You are affected only if you have a D-Link DIR-816 router running firmware version 1.10cnb05 with the web interface accessible and wireless repeater functionality present.

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

Replace the end-of-life D-Link DIR-816 device with a currently supported router, as no vendor patch will be released. If immediate replacement is infeasible, disable remote management interfaces and restrict network access to the device.

Recommended fix High confidence
  1. This vulnerability affects D-Link DIR-816 firmware version 1.10CNB05, which the official description explicitly states is a product 'no longer supported by the maintainer.'
  2. No patched firmware version, vendor patch, or upgrade path is available from D-Link for this end-of-life device.
  3. Replace the affected D-Link DIR-816 router with a currently supported device from D-Link or another vendor that receives active security updates.
  4. If replacement is not immediately possible, disable the wireless repeater functionality (goform/form2RepeaterStep2.cgi) or restrict access to the web management interface to trusted internal IPs only using external firewall rules.
  5. Monitor the vendor website periodically for any unexpected firmware releases, though none are currently indicated as available.
Caveat No upgrade path exists - D-Link DIR-816 is end-of-life and no longer supported. Replacement with a currently supported router is required.

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

Fix this in Dir 816 Firmware Scoped from the published advisory
  • Consultation6.0 h
  • Implementation8.0 h
  • Testing8.0 h
  • Review / QA4.0 h
26.0 hours of engineering $4,560
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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-2026-4181 in production — separate from our analysis above.

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What this is

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What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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