How severe is CVE-2021-26828?

CVE-2021-26828 has a CVSS score of 8.8/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-26828?

Affected package information for CVE-2021-26828 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2021-26828?

No fixed version has been published for CVE-2021-26828 yet. Monitor the advisory for updates, apply mitigations recommended by the vendor, and use O3 Security to track when a fix becomes available in your stack.

Is CVE-2021-26828 actively exploited in the wild?

Yes. There are 7 known exploit references for CVE-2021-26828, including 5 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-26828?

CVE-2021-26828 has an EPSS (Exploit Prediction Scoring System) score of 78.4%, placing it in the 99th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

Is CVE-2021-26828 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2021-26828 (OpenPLC ScadaBR Unrestricted Upload of File with Dangerous Type Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2025-12-03. CISA required all US federal civilian agencies to remediate this vulnerability by 2025-12-24. The required action was: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2021-26828?

CVE-2021-26828 is classified as Unrestricted File Upload (CWE-434). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Which products and versions are affected by CVE-2021-26828?

CVE-2021-26828 affects scadabr scadabr. Check the affected-products list on this page against your deployed version to confirm exposure.

When was CVE-2021-26828 published, and has it been updated?

CVE-2021-26828 was published on June 11, 2021 and was last updated on December 4, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2025-12-03 — agencies required to remediate by 2025-12-24

CVE-2021-26828

HIGH

OpenPLC ScadaBR through 0.9.1 on Linux and through 1.12.4 on Windows allows remote authenticated users to upload and execute arbitrary JSP files via view_edit.shtm.

Published

Jun 11, 2021

Updated

Dec 4, 2025

Affected

0 pkgs

Patched

None yet

Exploits

7 known

EPSS Exploitation Probability

via FIRST.org ↗

78.4%probability of exploitation in next 30 days

Very High Risk99th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Description

OpenPLC ScadaBR through 0.9.1 on Linux and through 1.12.4 on Windows allows remote authenticated users to upload and execute arbitrary JSP files via view_edit.shtm.

Affected Products

1 product · 2 configurations

Application

scadabrscadabr

≤ 1.12.4

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.