Cyber Resilience

CVE-2026-4621

Nec Aterm Wg1200Hp4 Firmware

Published
27 March 2026
Modified
20 April 2026
Patch / advisory
View advisory
CVSS Score v4 6.3
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.0016 5th percentile
Risk Priority 35 floored blend · peak EPSS

Summary

CVE-2026-4621 is a medium-severity Hidden Functionality (CWE-912) vulnerability in Nec Aterm Wg1200Hp4 Firmware. Its CVSS base score is 6.3 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Remote Services (T1021); ranked at the 5th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to CM-7 (Least Functionality) and SC-7 (Boundary Protection) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

Hidden Functionality vulnerability in NEC Platforms, Ltd. Aterm Series allows a attacker to enable telnet via network.

CWE(s)
CWE-912

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1021 Remote Services Lateral Movement
Adversaries may use [Valid Accounts](https://attack.
attack.mitre.org →
T1133 External Remote Services Persistence
Adversaries may leverage external-facing remote services to initially access and/or persist within a network.
attack.mitre.org →
Why these techniques?

Hidden functionality enables remote Telnet activation, directly mapping to remote services for access/persistence (T1021) and external remote services (T1133).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2026-4309Same product: Nec Aterm W1200Ex-Ms
CVE-2024-28011Same product: Nec Aterm W1200Ex-Ms
CVE-2026-4622Same product: Nec Aterm Wf1200Cr
CVE-2024-28015Same product: Nec Aterm W1200Ex-Ms
CVE-2024-28014Same product: Nec Aterm W1200Ex-Ms
CVE-2024-28005Same product: Nec Aterm W1200Ex-Ms
CVE-2024-28012Same product: Nec Aterm W1200Ex-Ms
CVE-2024-28009Same product: Nec Aterm W1200Ex-Ms
CVE-2024-28013Same product: Nec Aterm W1200Ex-Ms
CVE-2024-28006Same product: Nec Aterm W1200Ex-Ms

Affected Assets

nec
aterm wg1200hp4 firmware
all versions
nec
aterm wg2600hs firmware
≤ 1.7.2
nec
aterm wf1200cr firmware
≤ 1.6.0
nec
aterm wg1200cr firmware
≤ 1.5.0
nec
aterm wg2600hp4 firmware
≤ 1.4.2
nec
aterm wg2600hm4 firmware
≤ 1.4.2
nec
aterm wg2600hs2 firmware
≤ 1.3.2
nec
aterm wx3000hp firmware
≤ 2.5.0
nec
aterm wx3600hp firmware
≤ 1.5.3
nec
aterm w1200ex-ms firmware
all versions
+11 more product configuration(s) — see NVD for full list

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)
  • CM-7 Least Functionality
  • SC-7 Boundary Protection
  • AC-3 Access Enforcement
Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)

—

Mitigating Controls (NIST 800-53 r5) AI

CM-7 Least Functionality good match
prevent

Directly disables or prohibits unnecessary and non-essential functions such as Telnet that constitute the hidden functionality.

SC-7 Boundary Protection good match
prevent

Enforces boundary protection to block unauthorized network access paths used to enable the hidden Telnet service.

AC-3 Access Enforcement partial match
prevent

Enforces access control decisions so that hidden or undocumented functions cannot be activated without explicit authorization.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 full match
prevents

Secure SDLC practices directly prevent introduction of undocumented hidden functionality during development.

ID.RA-09 mostly match
prevents

Pre-acquisition integrity/authenticity checks can detect undocumented hidden functions in supplied software/hardware.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
detects

Security testing in development and acceptance can discover undocumented functionality before release.

A.8.32 Change management mostly match
prevents

Change management processes can catch unauthorized additions but do not inherently prevent hidden functionality from being introduced.

A.8.16 Monitoring activities partial match
detects

Monitoring activities can detect anomalous behavior from hidden functions but do not eliminate the weakness.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates documented requirements and design reviews that would expose undocumented hidden functionality.

A.8.26 Application security requirements partial match
prevents

Application security requirements explicitly define expected functionality, making hidden features a violation.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure system architecture and engineering principles require transparent, documented designs that preclude hidden functionality.

References