CVE-2021-20671Network attack vector

Arbitrary file overwrite via invalid upload validation

Published Mar 10, 2021 · Updated Aug 3, 2024

Improper input validation in GROWI 4.2.2 and earlier allows remote authenticated users to overwrite server files through uploads. The developer has not published the exact upload-handler locus or the validation operation that accepts attacker-controlled file paths. Administrative privileges are required, and a successful overwrite can place attacker-controlled content on the server and lead to arbitrary code execution.

CVSS severity7.6
High
EPSS probability1.84%
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 GROWI 4.2.2 and earlier allows remote authenticated users to overwrite server files through uploads. The developer has not published the exact upload-handler locus or the validation operation that accepts attacker-controlled file paths. Administrative privileges are required, and a successful overwrite can place attacker-controlled content on the server and lead to arbitrary code execution.

The record

CVE
CVE-2021-20671
Published
Mar 10, 2021
Updated
Aug 3, 2024
Vendor
WESEEK, Inc.
Product
GROWI
Classifications
CWE-20, T1190
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Mar 10, 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=versions v4.2.2 and earlier

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

WESEEK, Inc. · GROWIversion=versions v4.2.2 and earlier

Published CVSS scores

6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:P
7.6JPCERT/CCCVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:C/C:H/I:H/A:H
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)
Vectornetwork
Privilegesadmin
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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