Detect Marimo Remote Code Execution via Missing Authentication (CVE-2026-39987) in Sumo Logic CSE
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
Sumo Detection Query
_sourceCategory=*endpoint* OR _sourceCategory=*sysmon* OR _sourceCategory=*linux*
| where (process_name matches /(?i)marimo/ OR cmdline matches /(?i)marimo/)
| where cmdline matches /(?i)(subprocess|os\.system|exec\(|eval\(|Popen|shell=True|__import__)/
| count by host, user, process_name, cmdline
| fields host, user, process_name, cmdline, _count
| sort by _count descSumo Logic query filtering endpoint and sysmon logs for Marimo process invocations that include dangerous Python execution primitives, which may indicate exploitation of CVE-2026-39987.
Data Sources
Required Tables
False Positives & Tuning
- Researchers or analysts running notebooks that purposefully invoke shell commands for data processing
- Orchestration scripts that use Marimo as a scripting backend and call system utilities
- Automated regression tests that exercise Marimo's code execution API
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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