CVE-2021-26829
OpenPLC ScadaBR · Industrial and building systems
OpenPLC ScadaBR Cross-site Scripting Vulnerability
At a glance
Exploited. Added to CISA’s catalog of exploited vulnerabilities on November 28, 2025.
Affected product: OpenPLC ScadaBR (category Industrial and building systems, indicative classification). Name in CISA’s catalog: OpenPLC ScadaBR.
What should I do?
Apply the patches or mitigations from OpenPLC; if none are available, stop using the product. For cloud services, follow the guidance from OpenPLC.
Deadline set by CISA for US federal agencies: 21 days (due December 19, 2025). It only binds those agencies, but it is a useful measure of urgency.
- The vendor’s specific advisory is listed in the NVD references: CVE-2021-26829 on the NVD website.
Original text of the required action (CISA)
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Timeline
- Vulnerability published Publication date (NVD)
- Exploitation confirmed Added to CISA’s KEV catalog
- CISA deadline Remediation deadline set for US federal agencies
The facts, with their sources
- Exploitation confirmed
- Yes, on November 28, 2025 Date added to the catalog of exploited vulnerabilities. Exploitation itself may have started earlier. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- Ransomware
- No known use to date That does not guarantee it is not being used: the information is not public. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- Hunt for compromise
- Not requested by CISA Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- CISA required action
- Apply the patches or mitigations from OpenPLC; if none are available, stop using the product. For cloud services, follow the guidance from OpenPLC. Rewritten by this site from CISA’s original text. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- CISA deadline
- December 19, 2025, 21 days Set for US federal agencies: a measure of urgency, not an obligation elsewhere. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- Vulnerability published
- June 11, 2021 Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC
- Product according to CISA
- OpenPLC ScadaBR Filed by this site under “Industrial and building systems” (indicative classification). Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N Technical detail of the score: attack vector, complexity, impact. Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC
Severity and activity
FIRST’s EPSS model. Since exploitation is already confirmed, this figure is mostly useful to compare activity. Collected Sep 29, 2026.
Description
OpenPLC ScadaBR through 0.9.1 on Linux and through 1.12.4 on Windows allows stored XSS via system_settings.shtm.
Official description from the NVD, collected Sep 29, 2026. CVE® description © The MITRE Corporation.
OpenPLC ScadaBR contains a cross-site scripting vulnerability via system_settings.shtm.
Summary from CISA (KEV catalog).
CERT-FR advisories
No advisory among the latest CERT-FR publications this site follows. That does not mean there are none.
Information reused under the Open Licence 2.0 (Etalab); the date of last update is shown for each advisory. This site is neither affiliated with nor endorsed by ANSSI.
Sources for this page
- CISA KEV catalog: exploitation, date added, required action, deadline, ransomware.
- NVD (NIST): CVSS severity, publication date, description, vendor references.
- EPSS (FIRST): probability of exploitation.
- CERT-FR: advisories and alerts (in French).
- Brand and category: indicative classification by this site (method).