CVE-2019-5591

What is this vulnerability?

CVE-2019-5591 is categorized as a medium Missing Authentication for Critical Function flaw with a CVSS base score of 6.5. Based on our vulnerability intelligence, this issue occurs when the application fails to securely handle untrusted data boundaries.

A Default Configuration vulnerability in FortiOS may allow an unauthenticated attacker on the same subnet to intercept sensitive information by impersonating the LDAP server.

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-2019-5591

1. Apply Vendor Patches Immediately: This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog. Apply updates per vendor instructions.
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

A default configuration vulnerability in FortiOS allows an unauthenticated adjacent attacker to intercept sensitive information. Attackers impersonate LDAP servers due to missing TLS certificate validation. Precogs Application Security Module detects broken cryptographic verification and insecure defaults.

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.

Start scanning with Precogs →

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