InfoSecBulletin Cybersecurity for mankind
Cybersecurity and Infrastructure Security Agency (CISA) has mandated federal agencies to protect their industrial control systems due to active exploitation. CVE-2021-26829, a vulnerability in OpenPLC ScadaBR, is now included in the KEV Catalog.
This inclusion signals that threat actors are actively weaponizing this specific flaw to target operational technology (OT) environments.
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CVE-2021-26829 is a Stored XSS vulnerability in OpenPLC ScadaBR, impacting Linux versions up to 0.9.1 and Windows versions up to 1.12.4.
Stored XSS attacks are more dangerous than reflected XSS because they don’t need user interaction. They exploit vulnerabilities in the system_settings.shtm component, allowing attackers to store harmful scripts on the server. When an admin accesses the settings page, the script runs automatically in their browser.
In a SCADA system, attackers could take over admin sessions, alter industrial processes, or access sensitive OT networks.
The vulnerability is well-known in the security field. Researcher Fellipe Oliveira has shared a YouTube video demonstrating how to exploit it. This easy access to the exploit method may encourage less experienced hackers to take action, raising the need for a fix.
CISA has identified significant risks to federal operations and has mandated a compliance deadline. Federal Civilian Executive Branch agencies must address the identified flaw by December 19, 2025.
CISA urges all organizations, especially those managing critical infrastructure, to quickly patch this vulnerability to avoid disruptions, even though the mandate legally applies only to federal agencies.
