Most Common Vulnerabilities Found in Pentests
- Douglas Leal
- May 13
- 2 min read
Penetration tests are crucial for identifying weaknesses before attackers do. While every environment is unique, some vulnerabilities appear so frequently they’ve become cybersecurity classics.
In this article, we’ll explore the most common issues uncovered during pentests, how they work, and why they’re still widely exploited today.
1. Weak or Missing Authentication
Systems without proper authentication—or with poorly implemented login mechanisms—are easy targets.
Examples:
Default credentials (e.g., admin/admin)
Weak passwords or no complexity policies
Sensitive APIs with no authentication
JWTs without expiration
Impact: Unauthorized access to restricted areas or sensitive data.
2. Broken Access Control
Even when login works correctly, broken access control is one of the most critical and recurring flaws.
Examples:
Regular users accessing others’ data by changing IDs (IDOR)
Admin functions accessible without proper role checks
Misconfigured permissions in APIs or backend systems
Impact: Data leaks, privilege escalation, and unauthorized actions.
3. Code Injection (SQLi, XSS, Command Injection)
These classic flaws allow attackers to send inputs interpreted as actual commands by the system.
Common types:
SQL Injection: tamper with databases or exfiltrate data
XSS (Cross-Site Scripting): inject malicious scripts into web pages
Command Injection: execute OS-level commands on the server
Impact: Data breaches, session hijacking, and full system compromise.
4. Sensitive Data Exposure
When systems store or return personal/confidential data insecurely, the risk is huge.
Examples:
API responses exposing SSNs, emails, passwords, tokens
Unencrypted data at rest or in transit
No masking of sensitive fields in the UI
Impact: Data leaks, regulatory non-compliance (e.g., GDPR, LGPD), and reputational damage.
5. Security Misconfiguration
A top OWASP vulnerability—and for good reason. It’s easy to mess up.
Examples:
Exposed admin panels
Open or unnecessary network ports
Missing security headers (CSP, HSTS, etc.)
Poor container/service isolation
Impact: Unauthorized access, service exploitation, or DoS attacks.
6. Vulnerable Dependencies
Using outdated libraries or frameworks opens silent, dangerous holes.
Examples:
Components with known CVEs
No dependency management in Node, Python, Java projects
Exploitable vulnerabilities used in automated attacks
Impact: RCE, authentication bypass, injections, and more.
7. Session & Token Management Flaws
Poor session handling enables attackers to impersonate legitimate users.
Examples:
Sessions that never expire
JWTs signed with weak or no validation
Reusable sessions after logout
Impact: Session hijacking, unauthorized access, and system persistence.
8. Information Leakage in Errors and Logs
Detailed error messages are great for devs—and for attackers.
Examples:
Stack traces showing internal file paths or commands
Logs containing passwords, tokens, or request bodies
Verbose errors exposed to end users
Impact: Easier reverse engineering, system mapping, and data leaks.
How to Mitigate These Vulnerabilities
🔐 Best practices:
Enforce Multi-Factor Authentication (MFA)
Apply the Principle of Least Privilege
Sanitize and validate all inputs
Keep third-party components up to date
Use strong encryption in transit (TLS) and at rest
Run regular and in-depth pentests
Conclusion
These vulnerabilities persist because they’re often overlooked. Maintaining a proactive security posture with continuous testing and fast remediation processes is the best way to avoid serious incidents.
A well-executed pentest exposes blind spots before they become critical—and that’s pure gold for any business handling data or digital transactions.
