CVE-2021-26829: OpenPLC ScadaBR

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

Yes, if you run OpenPLC ScadaBR. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2025-11-28, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2025-12-19; treat that as the outer limit, not the target.
EPSS 48.0%, percentile 99: FIRST’s model estimates a 48.0% chance of exploitation activity in the next 30 days, higher than 99% of all scored CVEs (very high). EPSS is a probability, not a verdict.
Needs an account (low (any account)). Exposure depends on who can log in.

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

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

Weakness type: CWE-79.

Product: OpenPLC ScadaBR · Assigned by: mitre · Published: 2021-06-11

Vendor	Product	Affected versions (per CVE record)
n/a	n/a	see vendor advisory

Scored by	CVSS	Score	Vector
CISA-ADP	3.1	5.4 Medium	`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N`

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

CISA KEV: added 2025-11-28; federal due date 2025-12-19. Known ransomware use: Unknown.
CISA 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.
CISA SSVC assessment: exploitation active, automatable no, technical impact partial.
FIRST EPSS (model of 2026-10-21): 48.05% probability of exploitation activity in the next 30 days; percentile 99.

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.