Threats / OpenPLC / CVE-2021-26829
CVE-2021-26829
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
OpenPLC ScadaBR vulnerability
OpenPLC ScadaBR contains a cross-site scripting vulnerability in system_settings.shtm that allows injection of malicious scripts.
Verdict
Today item — known-exploited.
A reflected or stored XSS flaw in the system settings interface enables attackers to execute arbitrary JavaScript in administrator browsers, potentially leading to credential theft, session hijacking, or unauthorized configuration changes.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
6 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2025-11-28).
Probability (EPSS)
EPSS 0.4805 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: OpenPLC, ScadaBR. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-79 Cross-site Scripting (XSS) — weakness family: Web / client.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious URL or inject payload into system_settings.shtm parameters to execute JavaScript in the victim's browser.
Business
Administrative users are tricked into visiting attacker-controlled links or viewing compromised settings pages, exposing their session tokens and credentials.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I steal the administrator's session cookie or authentication token via the injected script.
Business
Attackers gain unauthorized access to the SCADA system with full administrative privileges, bypassing normal access controls.
3
Lateral reach — past segmentation narrative 3
Attacker
I modify system settings, disable security features, or inject persistent malicious code into the application.
Business
Critical infrastructure monitoring and control functions are compromised, enabling further lateral movement or operational disruption.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05