CVE-2021-22676Network attack vector

Browser script execution via UserExcelOut.asp input

Published Aug 10, 2021 · Updated Aug 3, 2024

Reflected XSS in Advantech WebAccess/SCADA before 8.4.5 and 9.0 through 9.0.0 allows remote attackers to run browser script. UserExcelOut.asp fails to neutralize attacker-supplied JavaScript before generating a web page. A user must open the crafted request; the script runs in that user's origin and can hijack session tokens, redirect the browser, or trigger unintended actions.

CVSS severity6.1
Medium
EPSS probability0.64%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in Advantech WebAccess/SCADA before 8.4.5 and 9.0 through 9.0.0 allows remote attackers to run browser script. UserExcelOut.asp fails to neutralize attacker-supplied JavaScript before generating a web page. A user must open the crafted request; the script runs in that user's origin and can hijack session tokens, redirect the browser, or trigger unintended actions.

The record

CVE
CVE-2021-22676
Published
Aug 10, 2021
Updated
Aug 3, 2024
Vendor
Advantech
Product
WebAccess/SCADA
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 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=WebAccess/SCADA versions prior to 8.4.5, WebAccess/SCADA versions prior to 9.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Advantech · WebAccess/SCADAversion=WebAccess/SCADA versions prior to 8.4.5, WebAccess/SCADA versions prior to 9.0.1

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

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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