CVE-2021-26829
OpenPLC — OpenPLC ScadaBR Cross-site Scripting Vulnerability
OpenPLC · CWE-79 — Cross-site scripting · in CISA KEV since 2025-11-28
EVRS 75 of 100 Urgent
Patch This Cycle
Rank 747 of 2,960 tracked
Raised to the floor for a confirmed exploited vulnerability.
Why it scores 75
Evidence available: 6 of 7 signalsListed in the CISA KEV catalog, and an EPSS probability of 0.480.
- CISA KEVApplied
- RansomwareDid not apply
- Vendor exploitationDid not apply
- EPSSApplied
- Microsoft Exploitability IndexNot applicable
- Pre-patch disclosureNo data
- KEV recencyDid not apply
- CVSSApplied
The band answers “how soon”, not “how bad”. No data for: Pre-patch disclosure. Why some signals show no data
Fix
Patch or fixed version identifiedCISA required action
- 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
- nvd.nist.gov/…/CVE-2021-26829
Fixed in
scadabr: update to a version newer than 0.9.1 | scadabr: update to a version newer than 1.12.4
Affected versions
- scadabr
<= 0.9.1<= 1.12.4 - linux kernel
- windows
Remediation
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Fixed versions from NVD.
Evidence
Each value with its source| Measure | Value | Source |
|---|---|---|
| CVSS base scoreHow severe the flaw is in itself. It does not say how likely an attack is. | 5.4 | NVD |
| FIRST EPSSFIRST's estimate of the chance this is exploited in the next 30 days, and how that ranks against all CVEs. | 0.480 (98.9th pctl) | FIRST EPSS |
| Actively exploitedWhether a source of record has confirmed attacks using it in the wild. | Confirmed | CISA KEV |
| Ransomware campaign useWhether CISA has seen ransomware operators use it. | Unknown or none | CISA KEV |
| CISA remediation deadlineThe date US federal agencies must have fixed or mitigated it. | 2025-12-19 · CISA federal deadline · Overdue by 10 months | CISA KEV |
| Public exploit moduleA module existing is not the same as active exploitation. | None known | Metasploit |
| EUVD cross-referenceENISA's record: CVSS 5.4 (v3.1), assigned by mitre. | Listed | ENISA EUVD |
Description
NVDOpenPLC ScadaBR through 0.9.1 on Linux and through 1.12.4 on Windows allows stored XSS via system_settings.shtm.
What CISA says to do