CVE-2021-26829Known exploitationPublic exploitNetwork attack vector

Stored XSS via system settings page

Published Jun 11, 2021 · Updated Dec 2, 2025

Stored XSS in OpenPLC ScadaBR 0.9.1 and earlier on Linux and 1.12.4 and earlier on Windows allows remote authenticated users to run scripts. The system_settings.shtm handler stores an unneutralized login-page description and later inserts it into rendered HMI content. Exploitation requires authenticated access to change system settings and a user to load the affected page, executing the stored script in that user's browser context.

CVSS severity5.4
Medium
EPSS probability48.05%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in OpenPLC ScadaBR 0.9.1 and earlier on Linux and 1.12.4 and earlier on Windows allows remote authenticated users to run scripts. The system_settings.shtm handler stores an unneutralized login-page description and later inserts it into rendered HMI content. Exploitation requires authenticated access to change system settings and a user to load the affected page, executing the stored script in that user's browser context.

The record

CVE
CVE-2021-26829
Published
Jun 11, 2021
Updated
Dec 2, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, CAPEC-592, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 11, 2021CVE publishedPublication date reported by the CVE source.
  2. Dec 2, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.4CISA ADPCVSS:3.1/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.

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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 exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CAPEC-592Stored XSS
T1059.007JavaScript/JScript

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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