CVE-2023-27351

What is this vulnerability?

CVE-2023-27351 is categorized as a high Improper Authentication flaw with a CVSS base score of 7.5. Based on our vulnerability intelligence, this issue occurs when the application fails to securely handle untrusted data boundaries.

This vulnerability allows remote attackers to bypass authentication on affected installations of PaperCut NG 22.0.5 (Build 63914). Authentication is not required to exploit this vulnerability. The specific flaw exists within the SecurityRequestFilter class. The issue results from improper implementation of the authentication algorithm. An attacker can leverage this vulnerability to bypass authentication on the system. Was ZDI-CAN-19226.

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-2023-27351

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.

Start scanning with Precogs →

Vulnerability Code Signature

Attack Data Flow

Vulnerable Code Pattern

// ❌ VULNERABLE: Improper Authentication
app.post('/login', (req, res) => {
  const { username, password } = req.body;
  // Taint sink: weak or bypassable validation
  if (username === 'admin' || password === 'secret') {
    req.session.authenticated = true;
    res.send('Logged in');
  }
});

Secure Code Pattern

// ✅ SECURE: Robust Authentication
const bcrypt = require('bcrypt');
app.post('/login', async (req, res) => {
  const { username, password } = req.body;
  const user = await db.getUser(username);
  // Sanitized validation: secure password comparison
  if (user && await bcrypt.compare(password, user.passwordHash)) {
    req.session.authenticated = true;
    res.send('Logged in');
  } else {
    res.status(401).send('Invalid credentials');
  }
});

How Precogs Detects This

Precogs API Security Engine comprehensively audits endpoints to ensure strict authentication boundaries and secure logic.\n