Avertium external penetration testing reveals an overlooked authentication gap through expert-led analysis and attack chaining.

STORY AT A GLANCE

  • Industry: Financial services

  • Engagement: External penetration test

  • Introduction:  A financial organization engaged Avertium to assess its external attack surface. By comparing the behavior of three VPN portals and validating subtle authentication differences, Avertium uncovered a certificate enforcement gap, weak administrator passwords, and an MFA misconfiguration that could have enabled unauthorized access.  

  • Challenge:  One of three VPN portals did not enforce the certificate requirement used by the other two portals 

  • Discovery: Expert-led testing exposed weak administrator passwords and an MFA configuration issue 

  • Security Impact: The combined weaknesses created a path that could be exploited for unauthorized access 

  • Differentiator: The finding depended on manual comparison, pattern recognition, and attack chaining rather than automated scanning alone  

The Challenge

The organization needed to understand whether its internet-facing systems could withstand a realistic attack and where gaps in security existed. It asked Avertium to conduct an external penetration test focused on identifying exploitable weaknesses that could expose the business to unauthorized access.

During attack surface analysis, Avertium identified three VPN portals protected by firewalls. Two required a certificate as part of authentication; the third did not. Although the difference was easy to overlook, it signaled that authentication controls were not being enforced consistently across the environment.

 

The Solution

Using open-source intelligence, Avertium’s penetration tester developed a targeted username list and performed a controlled password-spray test against the portal that lacked the certificate requirement. Two IT administrator accounts responded, and the testing indicated that both were protected by weak passwords.

Rather than treating the responses as isolated results, the tester recognized a pattern, paused, and then repeated the controlled test against the same accounts. The repeated behavior pointed to a deeper issue in the firewall or authentication workflow and warranted further validation.

 

VALIDATION OF THE MFA GAP

The customer notified Avertium after receiving multiple Duo push notifications generated by the test. This confirmed that the password spray was reaching the MFA stage. However, the MFA implementation was misconfigured, allowing the attack path to progress farther than intended.

 

WHY THE FINDING MATTERED

  • Inconsistent certificate enforcement reduced the protection of one VPN portal compared with the organization's other portals.
  • Weak administrator passwords increased the likelihood that credentials could be successfully tested or compromised.
  • Misconfigured MFA allowed authentication attempts to advance farther than expected instead of stopping the attack path.
  • Combined risk meant the weaknesses could be chained together to support unauthorized access.

 

CUSTOMER VALUE AND RECOMMENDED ACTIONS

Avertium gave the organization a clear view of how several individually subtle weaknesses could combine into a meaningful access risk. The findings provided actionable priorities: enforce certificate-based authentication consistently across all VPN portals, strengthen administrator password controls, correct the MFA configuration, and review firewall and authentication policies for consistency.

 

THE AVERTIUM DIFFERENCE

This engagement demonstrates the value of human-led penetration testing. An automated tool might have reported the portals and their exposed services, but the critical insight came from comparing configurations, recognizing an unusual response pattern, validating the behavior over time, and chaining the findings into a realistic attack scenario. That expert analysis turned a subtle configuration discrepancy into a prioritized security finding the customer could act on.

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