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CVE-2021-26829

Medium CVSS 5.4 Known exploited

Published 2021-06-11 · last changed 2026-06-17 · added to CISA KEV 2025-11-28

This one is being exploited in the wild.

CISA added CVE-2021-26829 to the Known Exploited Vulnerabilities catalog on 2025-11-28. Federal agencies are required to remediate it on a deadline. If you have affected machines, this is the class of finding that moves ahead of the rest of the queue.

The fix

We hold no Microsoft remediation data for CVE-2021-26829, which normally means it is not a Windows CVE. For non-Microsoft software the fix is the vendor's own updated release, and the affected versions are listed below.

What it is

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

Sources

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