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ExploitedIn CISA KEV

CVE-2021-26829

Exploitation confirmed. First attested on 2025-11-28 by CISA-ADP, CISA KEV, GCVE · kevintel.

  • Published2021-06-11
  • WeaknessCWE-79

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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

Timeline

dates in UTC
  1. 2021-06-1112:15CVE publishedNVD
  2. 2025-11-28Added to the CISA KEV catalogCISA KEV
  3. 2025-11-28Listed as exploited by GCVEGCVE
  4. 2025-11-28Exploitation first reportedCISA KEV
  5. 2025-12-01SSVC exploitation set to activeCISA-ADP

Observed activity

isMalicious corpus · updated 2026-11-04 09:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-26829?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-26829?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Scadabrversion to verify
BranchAffectedFixed in
0.9≤ 0.9.1no fix published
1.12≤ 1.12.4no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. CISA’s 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.due 2025-12-19

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub
Metasploit modules
none listed
Metasploit Framework

CISA Known Exploited Vulnerability

Date Added
2025-11-28
Patch Due Date
2025-12-19
Ransomware Use
Unknown
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.

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Published
2021-06-11
Last Modified
2026-06-17
NVD status
Analyzed
GitHub Advisory
GHSA-6pvv-xrf9-29m6

Frequently asked questions

What is CVE-2021-26829?

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

Is CVE-2021-26829 actively exploited?

Yes. CVE-2021-26829 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, meaning it has been confirmed as actively exploited in the wild. CISA requires federal agencies to patch by 2025-12-19.

What is the CVSS score for CVE-2021-26829?

CVE-2021-26829 has a CVSS v3 base score of 5.4 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

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Same product first, then the same vendor advisory and the same publication week.

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Sources for this record