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Dnr 202l FirmwareOperating system · Dlink

CVE-2026-4212

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 security vulnerability has been detected 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 affects the function Downloads_Schedule_Info of the file /cgi-bin/download_mgr.cgi. Such manipulation leads to stack-based buffer overflow. The attack can be launched remotely. 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 · moderate confidence

Stack-based buffer overflow vulnerability in the Downloads_Schedule_Info function of /cgi-bin/download_mgr.cgi allows remote attackers to execute arbitrary code on affected D-Link NAS devices (DNS-120, DNR-202L, DNS-315L, DNS-320 series, 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, DNS-1550-04). The vulnerability stems from insufficient bounds checking on user-supplied input processed by the download manager CGI script.

MitigationIf a vendor patch is unavailable, immediately restrict network access to affected devices, disable the download manager service if possible, and consider network segmentation. If the device cannot be patched or updated, replace with a supported alternative.

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 D-Link NAS model
    Access the device admin interface or check the device label to confirm the exact model (e.g., DNS-320, DNR-202L, DNS-326). Compare against the list of affected models provided in the CVE.
    Affected if Device model is one of: DNS-120, DNR-202L, DNS-315L, DNS-320 series, 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, DNS-1550-04.
  2. Check firmware version
    Log into the device web interface, navigate to the System/Status section, and record the firmware build date or version number. Alternatively, use the command line or check the firmware file metadata if you have firmware access.
    Affected if Firmware build date is 2026-02-05 or earlier for the identified model.
  3. Verify download manager CGI is accessible
    Attempt to access the URL path /cgi-bin/download_mgr.cgi on the device (e.g., http://<device-ip>/cgi-bin/download_mgr.cgi). A valid response (even an error) indicates the CGI is present.
    Affected if The download_mgr.cgi endpoint responds to HTTP requests, indicating the download manager component is installed.
  4. Confirm download manager feature is enabled
    In the device admin interface, look for Download Manager, Download Scheduler, or similar settings under Network or Storage sections. Check if the feature is toggled on or configured.
    Affected if The download manager feature is enabled or was previously configured on the device.
  5. Assess network exposure of the device
    Determine if the device web interface (port 80/443) is directly accessible from the internet or an untrusted network. Use external port scanning tools or review firewall rules.
    Affected if The device CGI interfaces are reachable from untrusted networks without VPN or firewall protection.

You are affected if you own a D-Link NAS model listed in the CVE, your firmware build date is 2026-02-05 or earlier, and the download manager CGI is accessible on your network.

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

If a vendor patch is unavailable, immediately restrict network access to affected devices, disable the download manager service if possible, and consider network segmentation. If the device cannot be patched or updated, replace with a supported alternative.

Fix this in Dnr 202l Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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-2026-4212 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