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 release is recorded for CVE-2021-26828 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.

How do I detect CVE-2021-26828 in my code and dependencies?

Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

How do I mitigate CVE-2021-26828 if there is no patch (or I can't update yet)?

Treat uploaded files as untrusted until proven otherwise: validate the actual content type rather than the supplied extension, store uploads outside the web root on a volume mounted without execute permission, and rename them to server-generated identifiers so an attacker cannot choose the path a request will later resolve.

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 39.1%, 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. This score warrants monitoring and prompt remediation.

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.

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 · ACTIVELY EXPLOITED

HIGH severity

CVE-2021-26828 — SCADA-LTS

HIGHFix: SCADA-LTS/Scada-LTS#2174

CVE-2021-26828 is a high-severity (CVSS 8.8) Unrestricted File Upload vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2025-12-03) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.

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

1 product

Patched

See advisory

Exploits

7 known

Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2025-12-03. Federal agencies were required to remediate by 2025-12-24.
A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2021-26828.

EPSS Exploitation Probability

via FIRST.org ↗

39.1%probability of exploitation in next 30 days

Moderate Risk-0.26%

Lower risk than most CVEs99th percentile — riskier than 99% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-26828 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 394,415 CVEs with a current EPSS score, this one falls in the 10–50% band (highlighted). Counts from FIRST.org, log-scaled.

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.