CVE-2026-39987

What is this vulnerability?

CVE-2026-39987 is categorized as a critical Missing Authentication for Critical Function flaw with a CVSS base score of 9.8. Based on our vulnerability intelligence, this issue occurs when the application fails to securely handle untrusted data boundaries.

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.

This architectural defect enables adversaries to bypass intended security controls, directly manipulating the application's execution state or data layer. Immediate strategic intervention is required.

Risk Assessment

Impact on Systems

✅ Unauthorized Data Access: Attackers can bypass authorization controls to access other users' data or administrative endpoints.

✅ Account Takeover: Broken authentication or authorization may enable full account compromise without valid credentials.

✅ API Abuse: Exploiting this vulnerability enables mass data harvesting or destructive operations through unprotected API endpoints.

How to Fix and Mitigate CVE-2026-39987

1. Apply Vendor Patches Immediately: This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
2. Verify Patch Deployment: Confirm all instances are updated using Precogs continuous monitoring.
3. Review Audit Logs: Investigate historical access logs for indicators of compromise related to this attack surface.
4. Implement Defense-in-Depth: Deploy WAF rules, network segmentation, and endpoint detection to limit blast radius.

Defending with Precogs AI

Precogs API Security Engine performs deep analysis of API endpoints using Code Property Graph traversal, detecting broken authentication, mass assignment, BOLA/IDOR, and SSRF vulnerabilities across REST, GraphQL, and gRPC interfaces before they reach production.

Use Precogs to continuously scan your codebase, binaries, APIs, and infrastructure for this vulnerability class and related attack patterns. Our AI-powered detection engine combines static analysis with threat intelligence to identify exploitable weaknesses before attackers do.

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Vulnerability Code Signature

Attack Data Flow

Vulnerable Code Pattern

// ❌ VULNERABLE: Missing Authorization (BOLA)
app.get('/api/users/:id/data', async (req, res) => {
  const userId = req.params.id;
  // Taint sink: fetches data for requested ID without verifying ownership
  const data = await db.getUserData(userId);
  res.json(data);
});

Secure Code Pattern

// ✅ SECURE: Strict Resource Authorization
app.get('/api/users/:id/data', requireAuth, async (req, res) => {
  const requestedId = req.params.id;
  const authenticatedId = req.user.id;
  
  // Sanitized validation: check ownership
  if (requestedId !== authenticatedId && !req.user.isAdmin) {
    return res.status(403).json({ error: "Unauthorized access" });
  }
  
  const data = await db.getUserData(requestedId);
  res.json(data);
});

How Precogs Detects This

Precogs API Security Engine comprehensively audits all exposed endpoints to guarantee strict session validation and resource authorization.\n