CVE-2021-20796Network attack vector

Arbitrary file upload via path traversal

Published Oct 13, 2021 · Updated Aug 3, 2024

Path traversal in the management screen of Cybozu Remote Service 3.1.8 allows remote authenticated users to upload arbitrary files. The management upload path fails to restrict a supplied pathname to its intended directory, but the affected handler and parameter are undisclosed. Management-screen access is required; the documented consequence is arbitrary server-side file placement, with no reported file execution.

CVSS severity4.2
Medium
EPSS probability1.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in the management screen of Cybozu Remote Service 3.1.8 allows remote authenticated users to upload arbitrary files. The management upload path fails to restrict a supplied pathname to its intended directory, but the affected handler and parameter are undisclosed. Management-screen access is required; the documented consequence is arbitrary server-side file placement, with no reported file execution.

The record

CVE
CVE-2021-20796
Published
Oct 13, 2021
Updated
Aug 3, 2024
Vendor
Cybozu
Product
Cybozu Remote Service
Classifications
CWE-22, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 13, 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=3.1.8

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Cybozu · Cybozu Remote Serviceversion=3.1.8

Published CVSS scores

4.9JPCERT/CCAV:N/AC:M/Au:S/C:N/I:P/A:P
4.2JPCERT/CCCVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L
4.0NIST NVDAV:N/AC:L/Au:S/C:N/I:P/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
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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