How severe is CVE-2021-26829?

CVE-2021-26829 has a CVSS 3.1 base score of 5.4 (MEDIUM). EPSS estimates a 48.0% probability of exploitation in the next 30 days. It is listed in the CISA Known Exploited Vulnerabilities catalog.

CVE-2021-26829: OpenPLC ScadaBR Cross-site Scripting Vulnerability

CISA Known Exploited Vulnerabilities

OpenPLC ScadaBR Cross-site Scripting Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.

Added to KEV

2025-11-28

Remediation due

2025-12-19

Required action
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

CISA notes
This vulnerability could affect an open-source component, third-party library, protocol, or proprietary implementation that could be used by different products. For more information, please see: https://github.com/SCADA-LTS/Scada-LTS/pull/3211 ; https://nvd.nist.gov/vuln/detail/CVE-2021-26829

Description

OpenPLC ScadaBR through 0.9.1 on Linux and through 1.12.4 on Windows allows stored XSS via system_settings.shtm.

Severity

CVSS 3.1 · CISA5.4 MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

SSVC · CISA-ADP

Exploitationactive

Automatableno

Technical impactpartial

Exploitation Context

as of October 17, 2026

All KEV statistics→

CISA added CVE-2021-26829 to the KEV catalog 1,631 days after its CVE record was published. The median for entries added in 2025 is 26 days.
It is one of 2 OpenPLC entries in the CISA KEV catalog, and one of 2 added in 2025.
Its current EPSS score (48.0%) is higher than that of 49% of CISA KEV entries.

Affected Products

Vendor	Product	Affected versions
-	-	n/a

References

2 Links

Other references

Record Details

Published

2021-06-11

Last updated

2025-12-02

Assigner (CNA)

mitre

Credited to

CVE record data © The MITRE Corporation, used under the CVE Terms of Use. Exploited-in-the-wild data from the CISA Known Exploited Vulnerabilities catalog (CC0). Exploit prediction scores by FIRST EPSS (first.org/epss). This site is not endorsed or certified by MITRE, NVD, CISA, or FIRST.