AUGUST 4, 2026
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Case File

CVE-2026-39987

CRITICAL · CVSS 9.8 EPSS 96.58% CISA KEV · Actively Exploited Public Exploit

Source: NVD + CISA KEV + EPSS (historical backfill) · Published 2026-04-09 · Last synced 2026-08-04

CyberRota Analysis

This is a critical severity vulnerability with a CVSS score of 9.8. It is listed in CISA's Known Exploited Vulnerabilities catalog, indicating confirmed active exploitation in the wild. Public exploit code or proof-of-concept references have been detected in its references. Its EPSS score suggests a 96.6% probability of exploitation in the next 30 days. Exploitation may require the attacker to be authenticated.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Note: these links are listed for security research and verification purposes only.

CISA KEV Details

Status: This CVE is listed in CISA's Known Exploited Vulnerabilities catalog.

Ransomware use: Unknown

Added to KEV: 2026-04-23

Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

CVE
CVE-2026-39987
Severity
CRITICAL
CVSS
9.8
EPSS
96.58%

Original NVD Description

marimo is a reactive Python notebook. Prior to 0.23.0, Marimo has a Pre-Auth RCE vulnerability. The terminal WebSocket endpoint /terminal/ws lacks authentication validation, allowing an unauthenticated attacker to obtain a full PTY shell and execute arbitrary system commands. Unlike other WebSocket endpoints (e.g., /ws) that correctly call validate_auth() for authentication, the /terminal/ws endpoint only checks the running mode and platform support before accepting connections, completely skipping authentication verification. This vulnerability is fixed in 0.23.0.