CVE-2021-20800Network attack vector

Authenticated script execution via management-screen XSS

Published Oct 13, 2021 · Updated Aug 3, 2024

Cross-site scripting in the management screen of Cybozu Remote Service 3.1.8 allows remote authenticated users to inject arbitrary scripts. Cybozu has not disclosed the affected parameter or the operation that fails to neutralize untrusted input before the management screen renders it. Exploitation requires product login and a logged-in user to view the affected content, allowing script execution in that user's browser context.

CVSS severity5.4
Medium
EPSS probability0.60%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in the management screen of Cybozu Remote Service 3.1.8 allows remote authenticated users to inject arbitrary scripts. Cybozu has not disclosed the affected parameter or the operation that fails to neutralize untrusted input before the management screen renders it. Exploitation requires product login and a logged-in user to view the affected content, allowing script execution in that user's browser context.

The record

CVE
CVE-2021-20800
Published
Oct 13, 2021
Updated
Aug 3, 2024
Vendor
Cybozu
Product
Cybozu Remote Service
Classifications
CWE-79
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

3.5JPCERT/CC and IPAAV:N/AC:M/Au:S/C:N/I:P/A:N
5.4JPCERT/CC and IPACVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/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-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

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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