CVE-2021-26829
OpenPLC ScadaBR Cross-site Scripting Vulnerability
Does this matter?
Known to be exploited in the wild (CISA KEV, CISA remediation deadline 19 December 2025). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.
Description
OpenPLC ScadaBR through 0.9.1 on Linux and through 1.12.4 on Windows allows stored XSS via system_settings.shtm.
- CVSS 3.1
- 5.4 MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
- EPSS
- 48.05% probability · 99th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Listed 28 November 2025 · due 19 December 2025
- Weakness
- CWE-79
- Affected
- scadabr/scadabr
- Source
- cve@mitre.org
EPSS 48.0% since 30 October 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
CISA notes
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. 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
References
- http://forum.scadabr.com.br/t/report-falhas-de-seguranca-em-versoes-do-scadabr/3615/4Vendor Advisory
- https://youtu.be/Xh6LPCiLMa8Exploit, Third Party Advisory
- http://forum.scadabr.com.br/t/report-falhas-de-seguranca-em-versoes-do-scadabr/3615/4Vendor Advisory
- https://youtu.be/Xh6LPCiLMa8Exploit, Third Party Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26829US Government Resource
- https://www.forescout.com/blog/anatomy-of-a-hacktivist-attack-russian-aligned-group-targets-otics/Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.