CVE-2021-20709

Administrative OS command execution via integrity-check bypass

Published Apr 26, 2021 · Updated Aug 3, 2024

Improper integrity validation in Aterm router firmware allows remote authenticated users to execute OS commands via a crafted request. The request-processing path accepts a crafted integrity-check value without proper verification, but public advisories do not identify the URL or function. Administrative access to the management screen is required, and successful exploitation gives command execution on the router.

CVSS severity6.8
Medium
EPSS probability0.66%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper integrity validation in Aterm router firmware allows remote authenticated users to execute OS commands via a crafted request. The request-processing path accepts a crafted integrity-check value without proper verification, but public advisories do not identify the URL or function. Administrative access to the management screen is required, and successful exploitation gives command execution on the router.

The record

CVE
CVE-2021-20709
Published
Apr 26, 2021
Updated
Aug 3, 2024
Vendor
NEC Platforms, Ltd.
Product
Aterm
Classifications
CWE-354, T1059
Attack vector
adjacent
Privileges
admin

Timeline

How it unfolded

  1. Apr 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Aterm WF1200CR firmware Ver1.3.2 and earlier, Aterm WG1200CR firmware Ver1.3.3 and earlier, and Aterm WG2600HS firmware Ver1.5.1 and earlier

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesadmin

What is affected?

NEC Platforms, Ltd. · Atermversion=Aterm WF1200CR firmware Ver1.3.2 and earlier, Aterm WG1200CR firmware Ver1.3.3 and earlier, and Aterm WG2600HS firmware Ver1.5.1 and earlier

Published CVSS scores

5.2JPCERT/CC and IPAAV:A/AC:L/Au:S/C:P/I:P/A:P
6.8JPCERT/CC and IPACVSS:3.0/AV:A/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
9.0NIST NVDAV:N/AC:L/Au:S/C:C/I:C/A:C
7.2NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-354Improper Validation of Integrity Check Value
T1059Command and Scripting Interpreter

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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