When organisations invest in cybersecurity, they often assume their defences are robust. However, CREST-accredited penetration testing regularly uncovers vulnerabilities that even the most diligent IT teams miss. These assessments provide an invaluable glimpse into how malicious actors might exploit weaknesses in your infrastructure, applications, and processes.
Understanding the most common security gaps that emerge during these rigorous examinations can help UK businesses proactively strengthen their defences. Let’s look at five vulnerabilities that consistently surface during professional security assessments.
1. Inadequate Patch Management and Outdated Systems
One of the most prevalent issues that penetration testing firms identify is outdated software and unpatched systems. Organisations struggle to maintain current versions across their entire digital estate, particularly when dealing with legacy applications or complex infrastructure.
These gaps create obvious entry points for attackers. Known vulnerabilities in older software versions often have publicly available exploits, making them low-hanging fruit for cybercriminals. The challenge intensifies when businesses run critical systems that can’t be easily updated without disrupting operations.
CREST testers frequently discover servers running obsolete operating systems, unpatched web applications, and firmware that hasn’t been updated in years. They’ll systematically probe these weaknesses to demonstrate the real-world risk they pose.
2. Weak Authentication and Access Controls
Authentication vulnerabilities remain surprisingly common, even in organisations that consider themselves security-conscious. Penetration tests regularly reveal accounts with default credentials, inadequate password policies, and missing multi-factor authentication on critical systems.
Testers often gain initial access through compromised credentials or by exploiting weak password requirements. Once inside, they frequently discover that users have excessive permissions, allowing lateral movement across networks and access to sensitive data that should be restricted.
The principle of least privilege is frequently violated. Employees, contractors, and service accounts often retain access rights long after they’re necessary, creating unnecessary risk. CREST assessments will highlight these over-permissioned accounts and demonstrate how they could be exploited.
3. Misconfigured Cloud Infrastructure
As UK businesses increasingly migrate to cloud platforms, misconfigurations have become a leading security concern. CREST penetration testers consistently find publicly accessible storage buckets, overly permissive security groups, and inadequately protected APIs.
These issues stem from the complexity of cloud environments and the shared responsibility model that many organisations don’t fully understand. A single misconfigured setting can expose vast amounts of sensitive data or provide attackers with a foothold in your environment.
Testers will examine your cloud architecture for exposed databases, improperly secured containers, and weak identity and access management policies. They’ll often discover that organisations have implemented security controls inconsistently across different cloud resources or regions.
4. Insufficient Network Segmentation
Many organisations operate with flat network architectures that allow unrestricted communication between different security zones. This creates significant risk because once an attacker breaches the perimeter, they can move freely throughout your environment.
CREST assessments regularly demonstrate how inadequate segmentation enables privilege escalation and lateral movement. Critical systems that should be isolated, such as payment processing environments or sensitive databases, are often accessible from less secure network segments.
Testers will map your network topology and identify where segmentation should exist but doesn’t. They’ll show how an initial compromise of a low-security system can rapidly escalate into access to your most valuable assets.
5. Vulnerable Web Applications
Despite widespread awareness of web application security, coding vulnerabilities continue to plague organisations. CREST penetration tests routinely uncover SQL injection flaws, cross-site scripting issues, and insecure direct object references in both customer-facing and internal applications.
These vulnerabilities often result from rushed development cycles, insufficient security testing, and developers who lack secure coding training. Third-party components and libraries introduce additional risk, particularly when they’re not regularly updated.
Testers will probe your web applications systematically, examining authentication mechanisms, input validation, session management, and API security. They’ll demonstrate how these flaws could be chained together to achieve significant compromise.
The Bottom Line
Identifying these security gaps is only the first step. CREST penetration testing firms provide detailed remediation guidance that helps you prioritise fixes based on risk and business impact.
The value lies not just in discovering vulnerabilities, but in understanding how they fit into your broader threat landscape. Regular assessments ensure that as your environment evolves, your security posture keeps pace with emerging threats and attack techniques.
By addressing these common gaps proactively, UK organisations can significantly reduce their attack surface and demonstrate due diligence to customers, regulators, and stakeholders.
