CVE-2021-20705Network attack vector

SYSTEM code execution via unvalidated WebManager upload

Published Nov 2, 2021 · Updated Aug 3, 2024

Improper input validation in NEC EXPRESSCLUSTER X 4.3 and earlier for Windows allows remote attackers to upload files through WebManager. The clpwebmc.exe web server accepts attacker-supplied binary data through UploadFile.js without validating the upload, leading to code execution as SYSTEM. The WebManager service listens on TCP port 29003 by default, so network access to the unauthenticated endpoint is sufficient.

CVSS severity7.5
High
EPSS probability1.11%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in NEC EXPRESSCLUSTER X 4.3 and earlier for Windows allows remote attackers to upload files through WebManager. The clpwebmc.exe web server accepts attacker-supplied binary data through UploadFile.js without validating the upload, leading to code execution as SYSTEM. The WebManager service listens on TCP port 29003 by default, so network access to the unauthenticated endpoint is sufficient.

The record

CVE
CVE-2021-20705
Published
Nov 2, 2021
Updated
Aug 3, 2024
Vendor
NEC Corporation
Product
EXPRESSCLUSTER X
Classifications
CWE-20, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 2, 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

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Is a vulnerable build present?

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

  1. Affected versionversion=CLUSTERPRO X 4.3 for Windows and earlier, EXPRESSCLUSTER X 4.3 for Windows and earlier, CLUSTERPRO X 4.3 SingleServerSafe for Windows and earlier, EXPRESSCLUSTER X 4.3 SingleServerSafe for Windows and earlier

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

NEC Corporation · EXPRESSCLUSTER Xversion=CLUSTERPRO X 4.3 for Windows and earlier, EXPRESSCLUSTER X 4.3 for Windows and earlier, CLUSTERPRO X 4.3 SingleServerSafe for Windows and earlier, EXPRESSCLUSTER X 4.3 SingleServerSafe for Windows and earlier

Published CVSS scores

5.0NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:N/I:P/A:N
7.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1190Exploit Public-Facing Application

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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