CVE-2026-4621
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 · uneditedHidden Functionality vulnerability in NEC Platforms, Ltd. Aterm Series allows a attacker to enable telnet via network.
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 confidenceThe Aterm Series devices contain undocumented hidden functionality that can be triggered remotely via network, allowing an attacker to enable the telnet service. This provides a backdoor for remote administrative access to the affected 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 dataall versions< 1.7.2< 1.6.0< 1.5.0< 1.4.2< 1.4.2< 1.3.2< 2.5.0CVSS 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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
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 checksWork through these to decide whether this CVE applies to you.
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Identify device modelLocate the device label on the Aterm router/modem or log into the web admin interface (typically http://192.168.0.1 or http://192.168.1.1) and check the device information page to confirm the exact model number (e.g., Wg1200hp4, Wg2600hs, Wf1200cr, etc.)Affected if The model matches any of the affected products: Wg1200hp4, Wg2600hs, Wf1200cr, Wg1200cr, Wg2600hp4, Wg2600hm4, Wg2600hs2, or Wx3000hp
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Check installed firmware versionIn the router web admin interface, navigate to the status or firmware information page and record the firmware version string. Compare it against the affected version ranges: Wg2600hs < 1.7.2, Wf1200cr < 1.6.0, Wg1200cr < 1.5.0, Wg2600hp4 < 1.4.2, Wg2600hm4 < 1.4.2, Wg2600hs2 < 1.3.2, Wx3000hp < 2.5.0. For Wg1200hp4, all versions are affected.Affected if The installed firmware version falls within or below the affected ranges listed, or for Wg1200hp4 any version is installed
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Scan for open telnet portUse a network port scanner (such as nmap) from an external host to scan the public IP address of the device: nmap -p 23 <device_ip>. Also scan from the internal network: nmap -p 23 <internal_ip>. Check if port 23/telnet is listening.Affected if Port 23/telnet is open and responding when it should not be enabled, especially on the WAN/public interface
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Check for unexpected remote management settingsIn the router web admin interface, review any remote management, remote access, or telnet settings pages. Look for options that enable telnet, WAN-side access, or undocumented features.Affected if Telnet service is enabled, or there is an unexpected setting allowing remote telnet access that was not intentionally configured by the administrator
The device is affected if it is any of the listed Aterm models running a firmware version within the affected ranges, or if port 23/telnet is unexpectedly open on the device.
Generated from the published advisory. Verify against your own configuration.
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 · scoped1.3.21.4.21.5.0
Apply vendor-provided firmware patches when available. Until then, disable telnet access at the network perimeter and monitor for unauthorized telnet port (23) exposure.
Model-specific firmware: Wg1200hp4 (latest), Wg2600hs (1.7.2+), Wf1200cr (1.6.0+), Wg1200cr (1.5.0+), Wg2600hp4 (1.4.2+), Wg2600hm4 (1.4.2+), Wg2600hs2 (1.3.2+), Wx3000hp (2.5.0+)
- 1. Identify the exact model of your Aterm device from the affected product list
- 2. Check the current firmware version of your device through the web management interface or device documentation
- 3. Download the latest firmware version from NEC's official support page at jpn.nec.com for your specific model
- 4. For Aterm Wg1200hp4: upgrade to the latest available firmware (all versions are affected)
- 5. For Aterm Wg2600hs: upgrade to firmware version 1.7.2 or later
- 6. For Aterm Wf1200cr: upgrade to firmware version 1.6.0 or later
- 7. For Aterm Wg1200cr: upgrade to firmware version 1.5.0 or later
- 8. For Aterm Wg2600hp4: upgrade to firmware version 1.4.2 or later
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-4621 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-4621 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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