Detect CVE-2021-26828: OpenPLC ScadaBR Unrestricted File Upload RCE in Sumo Logic CSE
Detects exploitation of CVE-2021-26828, an unrestricted file upload vulnerability in OpenPLC ScadaBR that allows authenticated attackers to upload files with dangerous types (e.g., JSP, PHP, WAR) to the server, leading to remote code execution. ScadaBR is a SCADA/HMI web application widely used in industrial control systems. This vulnerability is actively exploited in the wild and listed in CISA KEV.
MITRE ATT&CK
- Tactic
- Initial Access Execution Persistence
Sumo Detection Query
_sourceCategory=* ("scadabr" OR "openplc" OR "tomcat")
| parse "* * * \"* *\" * *" as client_ip, ident, auth_user, http_method, uri_path, response_code, bytes nodrop
| where http_method = "POST"
| where uri_path matches "/upload*" OR uri_path matches "/graphicViews*" OR uri_path matches "/images*"
| where uri_path matches "*.jsp" OR uri_path matches "*.jspx" OR uri_path matches "*.php" OR uri_path matches "*.war" OR uri_path matches "*.sh" OR uri_path matches "*.aspx"
| union (
_sourceCategory=*sysmon* OR _sourceCategory=*endpoint*
| json "event.action", "process.name", "process.parent.name", "process.command_line" as action, proc_name, parent_name, cmdline nodrop
| where action = "process_created"
| where parent_name matches "*java*" OR parent_name matches "*tomcat*"
| where proc_name in ("cmd.exe", "powershell.exe", "bash", "sh", "python", "python3", "nc", "wget", "curl")
)
| count by _sourceHost, client_ip, uri_path, http_method, proc_name, parent_name
| sort by _count descSumo Logic query identifying POST requests uploading dangerous file types to ScadaBR endpoints and Java processes launching shell interpreters, flagging potential CVE-2021-26828 exploitation.
Data Sources
Required Tables
False Positives & Tuning
- Authorized uploads of JSP-based custom dashboards by ScadaBR administrators
- Tomcat WAR deployment during maintenance windows by operations teams
- Java-based monitoring agents that spawn shell commands for health checks
- Authorized penetration testing activities targeting ICS/SCADA web interfaces
Other platforms for CVE-2021-26828
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Upload JSP Web Shell to ScadaBR Upload Endpoint
Expected signal: HTTP POST to /ScadaBR/upload.shtm with multipart form data containing .jsp file; Tomcat access log shows 200 response; file creation event for .jsp file in webapps directory
- Test 2Execute OS Command via Uploaded JSP Web Shell
Expected signal: Java process (Tomcat JVM) spawning child process for id, whoami, cat commands; Sysmon Event ID 1 with ParentImage containing java; process command line containing /etc/passwd
- Test 3Establish Reverse Shell from ScadaBR Server via Web Shell
Expected signal: Java process spawning bash with /dev/tcp redirect; outbound TCP connection from ScadaBR host to ATTACKER_IP:4444; network flow event with non-standard destination port from Java process
- Test 4Upload PHP Web Shell as Image File Bypass
Expected signal: POST request to upload endpoint with PHP file disguised as image; file creation event showing PHP content in webapps directory; Content-Type mismatch between declared image/jpeg and actual PHP content
Unlock Pro Content
Get the full detection package for CVE-2021-26828 including response playbook, investigation guide, and atomic red team tests.