Detect Marimo Remote Code Execution via Missing Authentication (CVE-2026-39987) in IBM QRadar
CVE-2026-39987 is a critical remote code execution vulnerability in the Marimo reactive notebook framework caused by missing authentication (CWE-306) for critical server-side functions. An unauthenticated remote attacker can invoke kernel execution endpoints to run arbitrary Python code in the context of the Marimo server process. This vulnerability is actively exploited in the wild and listed on the CISA KEV catalog.
MITRE ATT&CK
QRadar Detection Query
SELECT DATEFORMAT(starttime, 'YYYY-MM-dd HH:mm:ss') as event_time, sourceip, destinationip, destinationport, username, 'CVE-2026-39987' as cve_id, QIDNAME(qid) as event_name
FROM events
WHERE LOGSOURCETYPENAME(devicetype) IN ('LinuxAuth', 'MicrosoftWindows', 'SyslogUDP')
AND (
("Process Name" IMATCHES '.*marimo.*' AND "Command" IMATCHES '.*(subprocess|os\.system|exec|eval|Popen|shell=True).*')
OR (destinationport IN (2718, 8080, 8000) AND "Process Name" NOT IMATCHES '.*(marimo|python|python3).*')
)
LAST 24 HOURSQRadar AQL query identifying Marimo-related process events with dangerous Python execution patterns, or unexpected processes targeting Marimo's default ports, across Linux auth and Windows log sources.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate notebook workflows executing system commands via Python subprocess module
- Monitoring or health-check agents polling Marimo server ports
- Developers testing Marimo integrations with external tools on shared systems
- CI pipelines invoking Marimo kernels to validate notebook outputs
Other platforms for CVE-2026-39987
Testing Methodology
Validate this detection against 3 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 1Unauthenticated Marimo Kernel RCE via HTTP POST
Expected signal: HTTP POST to Marimo port 2718 from loopback or external IP; new child process (sh or bash) spawned under the Marimo/Python process; creation of /tmp/marimo_rce_test.txt by the Marimo server user
- Test 2Marimo RCE Reverse Shell Simulation
Expected signal: Outbound TCP connection from Marimo Python process to loopback port 9999; /bin/sh spawned as child of Python under Marimo server; socket.connect syscall in audit logs
- Test 3Marimo Persistence via Cron Injection through RCE
Expected signal: subprocess.run executing bash crontab command as Marimo server user; crontab modification event in audit logs; new cron entry for the Marimo user account
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