CVE-2026-4621 — Hidden Functionality vulnerability in NEC Platforms, Ltd. Aterm Series allows a attacker…

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

1. Identify exposed assets running the affected vendor/product/version combinations (Nec Aterm W1200ex-ms Firmware, Nec Aterm Wf1200cr Firmware, Nec Aterm Wg1200cr Firmware…).
2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
3. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
4. Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-912

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.25%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

• Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).

Timeline

What happened to this CVE, newest first.

• 2026
• Affected products added · nec platforms, ltd./aterm w1200ex(-ms), nec platforms, ltd./aterm wg1200hp2, nec platforms, ltd./aterm wg1900hp, nec pla
  Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
• SSVC assessment updated
  Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
• Record published
  Oct 13, 2026
• CVSS changed · 5.6
  Oct 13, 2026 · NIST National Vulnerability Database
• Source status changed · → Analyzed
  Oct 13, 2026 · NIST National Vulnerability Database
• Record created in this database
  Oct 13, 2026 · NIST National Vulnerability Database
• CVE published
  Mar 27, 2026 · NEC

Source activity

Repeated readings are counted rather than listed.

• 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

• jpn.nec.com/security-info/secinfo/nv26-001_en.html
  Vendor Advisory, NIST National Vulnerability Database

Elsewhere on this site

Related CVEs (same products)

• Critical CVE-2026-4622 OS Command Injection in Nec Aterm Wg2600hs Firmware Mar 27, 2026
• Medium CVE-2026-4309 Missing Authorization in Nec Aterm Wg2600hs Firmware Mar 27, 2026
• Critical CVE-2026-4619 Path Traversal in Nec Aterm Wx3600hp Firmware Mar 27, 2026
• Critical CVE-2026-4620 OS Command Injection in Nec Aterm Wx3600hp Firmware Mar 27, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

• No fixed version, patch or mitigation documented.
• No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
• No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
• No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-4621 is "Hidden Functionality vulnerability in NEC Platforms, Ltd. Aterm Series allows a attacker…", rated Medium. It affects Aterm W1200ex-ms Firmware (Nec); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.6 describes technical severity. EPSS 0.25% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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