Vulnerability

CVE-2021-26829

Medium· 5.4KEVCVSS5.4EPSS8%

.rules3/5

OpenPLC ScadaBR Cross-site Scripting Vulnerability

OpenPLC ScadaBR contains a cross-site scripting vulnerability via system_settings.shtm.

Threat signal

65/100

Elevated

Severity

medium

CVSS

5.4

EPSS

Active

KEV

CISA KEV — actively exploited

176d overdue

AffectedOpenPLC — ScadaBR

Added to KEV

2025-11-28

Federal patch due (BOD 22-01)

2025-12-19

Required action (CISA verbatim)

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Vendor advisory + references

CISA description: “OpenPLC ScadaBR contains a cross-site scripting vulnerability via system_settings.shtm.”

CVSS

v3.1Open in FIRST calculator →

5.4/ 10MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Attack VectorNetworkExploitable remotely over the internet — no local access needed.
Attack ComplexityLowNo special conditions — exploit works reliably.
Privileges RequiredLowStandard user privileges sufficient.
User InteractionRequiredRequires user action (click, file open, etc).
ScopeChangedImpact extends beyond the vulnerable component (e.g. sandbox escape).
Confidentiality ImpactLowSome data disclosure; attacker doesn't fully control what.
Integrity ImpactLowSome data modification; attacker doesn't fully control extent.
Availability ImpactNoneNo availability impact.

EPSS

Exploit prediction · 30-day horizonFIRST.org →

7.56%

probability of exploitation in next 30 days

p92

higher than 92% of all CVEs

3-day trend↑ 0pp

Mid-pack — moderate exploitation likelihood.

Vendor VEX

No VEX statements published for CVE-2021-26829. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.

SSVCAttend

Active exploitation with limited impact — coordinate patching

exploitation: active
automatable: no
impact: partial
mission: support

Lifecycle

2025-11-28Added to CISA KEVransomware: Unknown
2025-11-28Published
2025-12-19Federal patch due (BOD 22-01)
2026-06-12Last modified1 source

No source-event history recorded yet. New revisions will appear here as ingestors re-fetch this CVE.