Top 10 Vulnerabilities Found During Penetration Tests (and How to Fix Them)

In today's technology-driven business environment, cybersecurity stands as a critical priority for all organizations. Companies, regardless of size, face escalating threats from cyberattacks that often exploit known vulnerabilities. At Cyber Advisors, we conduct numerous penetration tests annually, empowering businesses to identify and rectify security gaps before they can be leveraged by malicious entities.

Below, we present the top 10 vulnerabilities most commonly discovered during penetration tests—and, more importantly, how to fix them. Whether you’re a small business or a large enterprise, understanding these flaws is the first step toward strengthening your security posture.

1.  Outdated Software and Unpatched Systems

Why It’s Dangerous

Outdated operating systems, third-party applications, or firmware create vulnerabilities that attackers can easily exploit. Public CVEs (Common Vulnerabilities and Exposures) serve as a treasure trove for those seeking to target unpatched systems.

How to Fix It

• Implement a Robust Patch Management Program: Regularly scan and update all software, including operating systems, applications, and plugins, to ensure they are up-to-date.
• Automate Updates: Utilize tools like WSUS (Windows Server Update Services) or third-party patching software to streamline and automate the update process.
• Prioritize Critical CVEs: Employ the CVSS (Common Vulnerability Scoring System) to identify and apply the most critical patches first, ensuring that the most significant vulnerabilities are addressed promptly.

2.  Weak or Default Passwords

Why It’s Dangerous
Attackers leverage automated tools and credential stuffing techniques to breach systems by guessing passwords or exploiting default credentials (such as "admin/admin"). Weak passwords are among the simplest entry points for unauthorized access.

• Enforce Robust Password Policies: Implement rules for minimum length, complexity, and expiration to enhance security.
• Implement Multi-Factor Authentication (MFA): MFA significantly diminishes the risk posed by compromised credentials.
• Utilize a Password Manager: Encourage users to create and securely store unique passwords.

3. Misconfigured Cloud Storage and Services

Why It’s Dangerous

Misconfigured cloud storage, such as AWS S3 or Azure Blob, poses significant risks by potentially exposing sensitive data to the public or granting unauthorized access to internal systems.

How to Fix It

• Implement Least Privilege Principles: Restrict access strictly to necessary personnel.
• Utilize Configuration Monitoring Tools: Employ solutions like AWS Config or Azure Security Center to identify and rectify misconfigurations.
• Activate Logging and Alerts: Continuously monitor for unusual activities and policy breaches in real-time.

4. Insecure Web Application Configurations
Why It’s Dangerous

Web applications are common targets for attacks. Missing security headers, verbose error messages, or outdated frameworks can open the door to exploits such as XSS, SQL injection, or remote code execution.

How to Fix It

• Strengthen Web Server Configurations: Eliminate directory listings and obscure software versions, and enforce HTTPS with essential headers such as HSTS and X-Content-Type Options.
• Execute Code Reviews and Web Application Scans: To detect web vulnerabilities effectively, utilize industry-standard tools like OWASP ZAP and Burp Suite.
• Deploy Web Application Firewalls (WAFs): These act as a barrier, filtering out malicious traffic before it can impact the application.

Unsecured or unnecessary services accessible from the internet create vulnerabilities that attackers can exploit to infiltrate your environment. Common examples include unsecured RDP, Telnet, or outdated FTP servers.

How to Fix It

• Conduct Regular Port Scans: Utilize tools such as Nmap or Nessus to identify open ports.
• Restrict Access: Implement firewalls, VPNs, or Zero Trust Network Access (ZTNA) to manage access to sensitive services.
• Segment the Network: Ensure critical systems are isolated from public-facing interfaces.

Excessive access rights can enable users, or attackers masquerading as users, to infiltrate systems or access data beyond their necessary scope. Privilege escalation vulnerabilities frequently arise from configuration errors or software defects.

How to Fix It

• Implement the Principle of Least Privilege (PoLP): Ensure users have access strictly aligned with their roles.
• Conduct Regular Permission Audits: Automate reviews to identify and rectify excessive access rights.
• Adopt Role-Based Access Control (RBAC): Establish roles and maintain consistent permissions across all systems.

Why It’s Dangerous: Flat network architectures allow attackers to move laterally within the environment, leading to a rapid spread of compromise across the network.

How to Fix It:

• Segment by Role or Function: Utilize VLANs, subnets, and firewalls to effectively isolate critical resources.
• Monitor Inter-Segment Traffic: Implement intrusion detection and prevention systems (IDS/IPS) between zones to enhance security.
• Implement Zero Trust Architecture: Consistently verify the legitimacy of users and devices at every access point.

Why It’s Dangerous
APIs are integral to modern applications and services, yet they frequently lack the robust security measures found in traditional interfaces. Common vulnerabilities include broken authentication, insufficient rate limiting, and excessive data exposure.

How to Fix It

• Authenticate and Authorize Every Call: Implement token-based authentication, such as OAuth2, and ensure permissions are validated.
• Limit Exposure: Restrict access to only necessary endpoints and data fields.
• Apply Rate Limiting and Logging: Implement measures to prevent abuse and monitor usage patterns to detect potential attacks.

Why It’s Dangerous: In the absence of a record, a breach can go undetected, hindering effective response. Without centralized logging and alert systems, organizations are likely to overlook early indicators of compromise (IOCs).

How to Fix It:

• Deploy SIEM Solutions: Utilize tools such as Splunk, ELK Stack, or Microsoft Sentinel to aggregate and analyze logs comprehensively.
• Enable Logging at All Layers: Ensure collection of logs from network, application, operating system, and security tools.
• Regularly Review Logs: To maintain robust security, automate alerts for suspicious activities and conduct manual reviews of critical assets.

Why It’s Dangerous: Even the most secure environments can fall prey to human error. Phishing, pretexting, and baiting attacks deceive users into divulging access or credentials.

How to Fix It:

• Continuous Security Awareness Training: Equip employees with the skills to identify and report suspicious emails or requests.
• Conduct Simulated Phishing Campaigns: Enhance user resilience through realistic testing.
• Deploy Technical Controls: Utilize email filtering, link scanning, and browser isolation to minimize exposure.

No single control can guarantee complete protection against breaches. The vulnerabilities outlined here underscore the critical need for a multi-layered defense strategy, where technical safeguards, process maturity, and user awareness collaborate to mitigate risks. At Cyber Advisors, we adopt a comprehensive approach to penetration testing.

Our assessments are meticulously customized to each client's unique environment, evaluating technical, procedural, and physical security aspects. Whether addressing external web applications, internal networks, cloud infrastructures, or social engineering tactics, our objective is to replicate real-world attack scenarios to identify vulnerabilities before adversaries can exploit them.

With decades of expertise, Cyber Advisors is dedicated to fortifying organizational security through our specialized penetration testing services. Our team, comprised of OSCP and CISSP-certified professionals, employs cutting-edge tools and methodologies to pinpoint vulnerabilities with precision and clarity. What Distinguishes Us:

• Tailored Testing: We customize each assessment to align with your business model, industry, and risk profile. • Transparent Reporting: We deliver actionable, clear findings with prioritized remediation strategies.
• Ongoing Support: Our consultants work closely with your team to address gaps and confirm fixes.
• Compliance Support: Our tests align with PCI-DSS, HIPAA, NIST, and ISO 27001 standards.

Expanding Our Expertise with Stratum Security, Cyber Advisors has recently acquired Stratum Security, a leader in advanced penetration testing and red teaming. This strategic move enhances our service offerings, strengthens our talent pool, and enables us to deliver even more innovative security assessments. Our commitment to continuous training, certifications, and threat intelligence ensures our clients benefit from a dynamic, highly effective security team that anticipates and counters emerging threats.

Proactively safeguard your organization by identifying and addressing vulnerabilities before they are exploited. Contact Cyber Advisors today to arrange a consultation or a customized penetration test that aligns with your specific requirements.