Detect Marimo Remote Code Execution via Missing Authentication (CVE-2026-39987) in CrowdStrike LogScale
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
LogScale Detection Query
event_simpleName IN ("ProcessRollup2", "SyntheticProcessRollup2")
| search FileName="python" OR FileName="python3" OR CommandLine=~"marimo"
| eval is_marimo_parent = if(match(ParentBaseFileName, "(?i)marimo"), 1, 0)
| eval is_rce_pattern = if(match(CommandLine, "(?i)(subprocess|os\.system|exec\(|eval\(|Popen|shell=True|__import__|pty\.spawn)"), 1, 0)
| where is_marimo_parent=1 AND is_rce_pattern=1
| stats count by ComputerName, UserName, FileName, CommandLine, ParentBaseFileName
| eval ThreatLabel = "CVE-2026-39987 Marimo Unauthenticated RCE"CrowdStrike CQL query identifying Python processes spawned under a Marimo parent that contain shell execution or code injection patterns, consistent with unauthenticated kernel RCE exploitation.
Data Sources
Required Tables
False Positives & Tuning
- Notebook code that legitimately calls subprocess or os.system for scientific computing tasks
- Marimo extensions that spawn helper Python processes with eval or exec during normal operation
- Automated notebook runners that exercise Marimo code execution endpoints in CI environments
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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