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Dnr 202l FirmwareOperating system · Dlink

CVE-2026-4207

CRITICAL · 9.8 CVSS v3.1 Published 2026-03-16
Fix available
A fix is available. Upgrade to after 2026-02-05 or later.
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 vulnerability was determined in D-Link DNS-120, DNR-202L, DNS-315L, DNS-320, DNS-320L, DNS-320LW, DNS-321, DNR-322L, DNS-323, DNS-325, DNS-326, DNS-327L, DNR-326, DNS-340L, DNS-343, DNS-345, DNS-726-4, DNS-1100-4, DNS-1200-05 and DNS-1550-04 up to 20260205. This impacts the function cgi_device/cgi_sms_test/cgi_firmware_upload/cgi_ntp_time of the file /cgi-bin/system_mgr.cgi. Executing a manipulation can lead to command injection. The attack may be performed from remote. The exploit has been publicly disclosed and may be utilized.

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

Multiple D-Link NAS and camera recorder devices contain a command injection vulnerability in /cgi-bin/system_mgr.cgi through functions cgi_device, cgi_sms_test, cgi_firmware_upload, and cgi_ntp_time. Attackers can inject arbitrary OS commands via these CGI endpoints due to insufficient input validation, potentially achieving full device compromise with root-level privileges.

MitigationApply vendor-supplied firmware patches when available; prior to patching, restrict network access to affected devices, disable the vulnerable CGI endpoints if possible, and monitor for indicators of compromise. Consider device replacement if patches are unavailable since these are legacy devices.

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
Dnr 202l FirmwareOperating system
Affected:<= 2026-02-05
Dnr 326 FirmwareOperating system
Affected:<= 2026-02-05
Dns 1100 4 FirmwareOperating system
Affected:<= 2026-02-05
Dns 120 FirmwareOperating system
Affected:<= 2026-02-05
Dns 1200 05 FirmwareOperating system
Affected:<= 2026-02-05
Dns 1550 04 FirmwareOperating system
Affected:<= 2026-02-05
Dns 315l FirmwareOperating system
Affected:<= 2026-02-05
Dns 320 FirmwareOperating system
Affected:<= 2026-02-05

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 the D-Link device model
    Access the device web interface or check the device label/console to confirm the exact model (Dnr 202l, Dnr 326, Dns 1100 4, Dns 120, Dns 1200 05, Dns 1550 04, Dns 315l, or Dns 320)
    Affected if The device model matches one of the listed affected products
  2. Check the installed firmware version
    Log into the device web interface (usually under System or Maintenance settings) or use the device's web API to retrieve the current firmware build date. Compare against the affected date 2026-02-05
    Affected if The firmware build date is on or before 2026-02-05
  3. Verify if the vulnerable CGI endpoint is accessible
    Attempt to access https://<device_ip>/cgi-bin/system_mgr.cgi from an authorized internal network location to confirm the endpoint responds
    Affected if The device responds to requests at /cgi-bin/system_mgr.cgi and the device is on the network with the vulnerable firmware version
  4. Look for indicators of compromise
    Check for unexpected new user accounts, unfamiliar processes, or modified system files that may indicate the device has been compromised through this command injection vulnerability
    Affected if Signs of unauthorized access or device compromise are found on an affected device

The device is affected if it is one of the listed D-Link models (Dnr 202l, Dnr 326, Dns 1100 4, Dns 120, Dns 1200 05, Dns 1550 04, Dns 315l, or Dns 320) running firmware dated 2026-02-05 or earlier.

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
Upgrade available Upgrade to a release after 2026-02-05
Interim mitigation

Apply vendor-supplied firmware patches when available; prior to patching, restrict network access to affected devices, disable the vulnerable CGI endpoints if possible, and monitor for indicators of compromise. Consider device replacement if patches are unavailable since these are legacy devices.

Fix this in Dnr 202l Firmware Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing12.0 h
  • Review / QA8.0 h
44.0 hours of engineering $7,720
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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-2026-4207 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