Threats / OpenPLC / CVE-2021-26828
CVE-2021-26828
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
OpenPLC ScadaBR vulnerability
OpenPLC ScadaBR allows authenticated users to upload arbitrary JSP files through view_edit.shtm, enabling remote code execution on the affected system.
Verdict
Today item — known-exploited.
An authenticated attacker can bypass file upload restrictions to execute arbitrary code on the server. This vulnerability has been exploited in the wild and poses significant risk to operational technology environments running ScadaBR.
CISA KEV Yes · 2025-12-034EPSS 0.39356 (verify live)5Exploit Public PoC6CVSS 8.8 (CISA)3CISA SSVC Exploitation: active · Automatable: no · Impact: total3
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Public proof-of-concept exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
5 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 2025-12-03).
Probability (EPSS)
EPSS 0.39356 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 8.8 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) · Affected: OpenPLC, ScadaBR. Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-434 Unrestricted File Upload — weakness family: Path traversal / file.CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: totalCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 1636 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
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 authenticate to the ScadaBR application using valid credentials.
Business
Legitimate user accounts or weak authentication controls provide initial access to the system.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I craft a malicious JSP file and submit it through the view_edit.shtm upload function.
Business
File upload validation fails to restrict dangerous executable file types.
3
Lateral reach — past segmentation narrative 3
Attacker
I execute the uploaded JSP file by accessing it through the web server.
Business
The JSP file executes with application privileges, compromising system integrity.
4
Data at risk — exfiltration narrative 4
Attacker
I establish persistent access or pivot to connected industrial control systems.
Business
Operational technology infrastructure becomes compromised, risking production disruption and safety.
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
Coverage & confidence
— what we know, and what we don’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by mitreCNA
Credited with finding itNo finder is named in the public CVE record or the scanned vendor advisory — attribution scoped to the sources checked.
Found an error? Propose a correction.
A correction is a cited counter-claim — it must cite a source,
gets reviewed by a second human, and is never auto-applied. See the
correction convention and our identity
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