Hackers have begun exploiting a critical remote code execution (RCE) vulnerability in the Marimo open-source Python notebook platform just 10 hours after its public disclosure. Tracked as CVE-2026-39987 with a CVSS score of 9.3, the flaw resides in the /terminal/ws WebSocket endpoint, which fails to implement proper authentication. This oversight allows unauthenticated attackers to gain direct access to a full interactive shell with the same privileges as the Marimo process.
According to Sysdig researchers, the attacks involve manual reconnaissance rather than automated scripts, focusing on high-value targets such as .env files and SSH keys. Although Marimo has released version 0.23.0 to address the issue, users who cannot immediately upgrade are advised to block access to the vulnerable endpoint or restrict network exposure to prevent sensitive data exfiltration and unauthorized system access.
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