CVE-2021-26829
MediumExploitedPublic exploitOpenPLC ScadaBR through 0.9.1 on Linux and through 1.12.4 on Windows allows stored XSS via system_settings.shtm.
Published Jun 11, 2021 · Updated Dec 2, 2025
Key Facts
Patch immediately- CVE-2021-26829 is a medium-severity vulnerability (CVSS 5.4 v3.1) affecting Scadabr.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Oct 9, 2025. Public exploit code is available.
- EPSS estimates a 48% probability of exploitation in the next 30 days.
- Fixed versions are available, including Scadabr <=0.9.1, Scadabr 0.9.1.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
5.4
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
EPSS (30-day exploit likelihood)
48%
Higher than 98.8% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2021-26829 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
Description
OpenPLC ScadaBR through 0.9.1 on Linux and through 1.12.4 on Windows allows stored XSS via system_settings.shtm.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Nov 28, 2025 | Dec 19, 2025 | Not reported |
| Industry KEV feed | Oct 9, 2025 | Dec 19, 2025 | Not reported |
| CIRCL KEV | Nov 28, 2025 | Dec 19, 2025 | Not reported |
| ENISA EUVD | Nov 28, 2025 | n/a | Not reported |
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.
Affected Products
1 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| ScadabrScadabr | See advisory | 0.9.1 |
Patched Releases
Scadabr
<=0.9.1
Timeline
Publicly disclosed
Jun 11, 2021
Added to Industry KEV feed
Oct 9, 2025
Added to CISA KEV
Nov 28, 2025
Added to CIRCL KEV
Nov 28, 2025
Added to ENISA EUVD
Nov 28, 2025
Last updated
Dec 2, 2025
Weakness Type
- CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
References
- advisoryhttp://forum.scadabr.com.br/t/report-falhas-de-seguranca-em-versoes-do-scadabr/3615/4
- advisoryVulnCheck exploitation report
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
FAQ
Common Questions.
OpenPLC ScadaBR through 0.9.1 on Linux and through 1.12.4 on Windows allows stored XSS via system_settings.shtm.
Affected: Scadabr. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Oct 9, 2025.
Yes. It was added on Nov 28, 2025 with a federal remediation due date of Dec 19, 2025.
Public exploit code is available.
Fixed versions are available, including Scadabr <=0.9.1, Scadabr 0.9.1.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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