CVE-2021-26828
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.
do firstApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Can a WAF block it? Partly. The vulnerability involves authenticated users uploading JSP files through a specific web interface page, which is an unusual and identifiable action that a web application firewall can detect and block. A WAF rule can match upload of JSP files via view_edit.shtm. No tracked WAF vendor has published a rule for this CVE yet, so you would write it yourself.
What a custom rule would match: upload of JSP files via view_edit.shtm
Also consider: patch · custom WAF rule · MIME sniff · sandbox storage
Based on an AI reading of the CVE description, and no vendor rule found yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Is CVE-2021-26828 being exploited?
Yes. CVE-2021-26828 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2021-26828?
CVE-2021-26828 is rated High with a CVSS score of 8.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2021-26828?
Yes. A fix has been recorded for CVE-2021-26828. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2021-26828 affect?
CVE-2021-26828 affects scadabr:scadabr. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
public exploits
Unvetted proof-of-concept code on GitHub: 3 GitHub proofs of concept
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
cisa ssvc
- exploitation
- active
- automatable
- no
- technical impact
- total
Assessed by CISA 3 Dec 2025 (SSVC 2.0.3).
timeline
- 31 Mar 2021First proof-of-concept repository on GitHub (unvetted)
- 11 Jun 2021Published · 73 days (about 2 months) later
- 3 Dec 2025Added to CISA KEV (exploited in the wild) · 1,635 days (about 4 years) later
- 3 Dec 2025CISA SSVC assessment: exploitation active · same day later
- 4 Dec 2025CVE record last updated · 1 day later
- 24 Dec 2025CISA remediation due date (US federal agencies) · 20 days later
- 2 Nov 2026Analysed by vulneraibility.com · 314 days (about 10 months) later
- Linkyoutu.be /k1teIStQr1A
- Linkpacketstormsecurity.com /files/162564/ScadaBR-1.0-1.1CE-Linux-Shell-Upload.html
- Linkforum.scadabr.com.br /t/report-falhas-de-seguranca-em-versoes-do-scadabr/3615/4
- Linkcisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26828
- Linkgithub.com /SCADA-LTS/Scada-LTS/pull/2174
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- PoC-in-GitHub: GitHub repositories that claim a proof of concept
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.