What Is a Security Vulnerability and How It Works

What Is a Vulnerability in Cybersecurity?

A vulnerability is a weakness or flaw in software code, system configuration, or operational process that can be exploited by a threat actor to gain unauthorized access, disrupt services, or exfiltrate sensitive data. Vulnerabilities directly impact the confidentiality, integrity, or availability (CIA) of an information system.

Most Common Types of Security Vulnerabilities 

Below are some of the most prevalent types of vulnerabilities found across both enterprise and small-to-medium-sized business environments.

• Unpatched software bugs, such as CVE-2025-22457, a critical remote code execution flaw in Ivanti Connect Secure VPN appliances actively exploited by advanced threat actors.

• Misconfigured cloud services, like open Amazon S3 buckets, unrestricted Azure Blob storage, or unsecured public APIs that unintentionally expose sensitive data.

• Weak access controls, including default credentials, disabled or missing multi-factor authentication (MFA), and overly permissive IAM roles or Active Directory group policies.

• Credential exposures, such as Kerberoastable service accounts using weak or guessable passwords, which can be cracked offline to gain lateral movement or privilege escalation.

• Unsafe communication protocols, like unencrypted HTTP, expired TLS certificates, or use of deprecated SSL versions, which allow interception or tampering with data in transit.

• Insecure software configurations, such as directory listing enabled on web servers, exposed admin panels, or lack of input sanitization leading to injection attacks.

Not all vulnerabilities are actively exploited, but every cyberattack starts with one or more of these weaknesses. Identifying vulnerabilities is only the first step. Determining whether they are exposed and exploitable in your environment is what defines real risk, and should guide prioritization efforts.

The following sections explore the legacy frameworks used to prioritize remediation efforts for security vulnerabilities, including CVSS, EPSS, and CISA’s KEV catalog.

CVSS, EPSS and KEV: What Makes a Security Vulnerability Critical in Legacy Terms

Legacy scoring frameworks like CVSS, EPSS, and CISA’s KEV define a “critical” vulnerability as one that combines high technical severity with credible threat indicators. 

These systems were developed to create a shared taxonomy and scoring model for classifying vulnerabilities and guiding remediation priorities. In essence, they represent structured attempts to help security teams focus limited resources on the issues that appear most urgent. Thus, sadly, they are based on standardized but largely theoretical criteria.

So, let’s investigate each of these legacy prioritization frameworks one by one.

Common Vulnerability Scoring System (CVSS)

CVSS is currently at version 3.1 with version 4.0 underway. It assigns a critical rating to vulnerabilities scoring near the top of the 0–10 scale (typically ≥9.0) based on general exploitability and impact characteristics. 

While CVSS includes Environmental metrics to account for factors like asset value and exposure in a specific organization, these inputs are subjective, manually set, and disconnected from real-time control effectiveness, making them insufficient to reflect dynamic exploitability.

Exploit Prediction Scoring System (EPSS)

EPSS is now in version 4. It enhances prioritization by estimating the probability that a vulnerability will be exploited in the wild.

The thing with EPSS is that it is a global statistical model based on factors like CVE age and public exploit availability. Hence, it does not consider whether an exploit would actually succeed in your environment, given your compensating controls, detection capabilities, or segmentation.

CISA’s Known Exploited Vulnerabilities (KEV) 

CISA’s KEV list highlights vulnerabilities that are already under active exploitation. 

While highly useful for raising awareness of immediate threats, KEV is binary and universal. So, it tells you what is being exploited globally, not whether that threat path exists in your environment or whether your controls already mitigate it.

Even when used together, these frameworks provide a view of potential risk, not validated risk. 

They lack direct measurement of control effectiveness or adversary success within a specific organizational context—leaving defenders to make critical decisions without evidence of actual exploitability.

What Makes a Vulnerability Exploitable in Real-World Environments

A vulnerability becomes exploitable when the conditions exist for it to be practically used by an attacker to achieve an objective, such as initial access, privilege escalation, or lateral movement. It’s not enough for a vulnerability to be severe in theory; it must also be reachable and usable within the specific context of the target environment.

That context includes:

• Exploit availability: Whether reliable exploit code exists

• Attack surface exposure: Whether the vulnerable component is externally accessible or internally reachable

• Security control effectiveness: Whether existing defenses (e.g., SIEM, IPS, EDR, segmentation, etc.) detect or block the attack

• Asset importance: Whether exploitation leads to meaningful impact

Example 1: How a CVSS 9.0 Vulnerability Turns Out to Be Non-Exploitable

Let’s look at a hypothetical yet highly realistic scenario to better understand how a vulnerability can be exploited.

Note that in the same manner, a medium-severity vulnerability with no protections in place could be exploited immediately to pivot toward high-value assets. So, check out another example.

Example 2: How an Internal CVSS 6.5 Vulnerability Posed Greater Risk Than a 9.0

With these two examples illustrating how theoretical severity can mislead prioritization, let’s examine how unaddressed vulnerabilities translate into real-world breaches

Relation Between Vulnerabilities and Data Breaches

Critical vulnerabilities that remain unpatched present more than just theoretical risk. They are actively leveraged by attackers using post-exploit automation tools, commodity malware, and ransomware kits. 

Average Time-to-Exploit a Vulnerability

Once proof-of-concept code is made public, the time between disclosure and real-world exploitation continues to shrink. 

In 2024, the average time-to-exploit dropped to approximately five days, down from thirty-two days the year prior [1]. This compression of the exploitation window leaves little room for delayed remediation.

When a Vulnerability Leads to a Data Breach

The consequences of inaction are reflected in breach data, too.

According to the 2024 Verizon Data Breach Investigations Report, fourteen percent of breaches were directly attributed to attackers exploiting known, unpatched vulnerabilities. This figure was nearly three times higher than in the previous year, underscoring the tangible risk posed by delayed or incomplete vulnerability management [2].

In practice, the challenge is not simply identifying vulnerabilities, but determining which ones represent real, actionable risk within your environment. Vulnerability scanners may return thousands of findings with critical CVSS and EPSS scoring, but treating them all as equal quickly becomes unmanageable. 

Without the ability to understand exploitability in context, organizations are left playing a constant and unsustainable game of Whack-a-Mole with CVEs: burning resources on perceived threats while actual risks persist.

The Vulnerability Surge: We Are Drowning in CVEs

Well, the vulnerability landscape has reached a breaking point. 

In 2024 alone, over 40,000 new CVEs were published. This is the largest volume in a single year to date. That’s an average of 110 vulnerabilities per day, many demanding immediate attention.

More than 61% were labeled high or critical, automatically triggering internal response policies and SLA clocks across enterprise environments. In many organizations, a critical vulnerability comes with a 24-hour SLA—patch or mitigate within a day, or risk non-compliance.

The result? Unrelenting pressure on security teams to act fast, regardless of whether the threat is real or relevant.

SOC analysts, vulnerability managers, and infrastructure teams are overwhelmed—not because they lack discipline or tooling, but because the system is saturated. Thousands of vulnerabilities, limited resources, and escalating urgency lead to:

• Patch queues that spiral out of control
• SLA violations and audit risks
• Burnout and alert fatigue

And yet, the paradox persists: only a small fraction of these vulnerabilities are ever exploited, and even fewer succeed in defended environments.

The problem isn’t just scale. It's a lack of context. Without knowing which vulnerabilities are truly exposed and exploitable, teams are forced to treat every CVE like a crisis.

Why You Can’t Patch All of Your “Critical” Vulnerabilities

The idea that every so-called “critical” vulnerability that is output by your vulnerability scanners and assessment tools must be patched immediately is not only unrealistic; it is operationally unsustainable. In modern enterprise environments, patch queues often number in the thousands, especially in organizations with complex infrastructure, multiple business units, and legacy systems that still play a critical role in day-to-day operations.

Even with an unlimited security budget and a thousand-person IT staff, large-scale emergency patching would bring core business systems to a halt. Frequent reboots, validation cycles, and regression testing introduce downtime, disrupt service delivery, and increase the risk of failure. This is especially true in sectors where system availability is essential.

Pathing Your Vulnerability: Legacy Constraints and the Illusion of Urgency

And that assumes every asset is patchable.

Many organizations still rely on legacy hardware, unsupported software, or industrial systems that cannot be updated safely or are no longer supported by vendors. In these environments, traditional patching is not just inefficient. It is often impossible.

Despite these constraints, vulnerability scanners and legacy risk scoring systems continue to flag every high CVSS vulnerability as urgent, regardless of exploitability in the actual environment. These tools provide scale but not clarity. 

This reflects a fundamental operational challenge: theoretical severity does not equal actual risk. 

What is needed is proof of exploitability, which is direct evidence that a vulnerability can be executed within your environment, bypassing your defenses and leading to impact. Only with this level of validation can organizations prioritize accurately, minimize wasted effort, and shift from reactive patching to focused risk reduction.

Proof of Exploitability in Traditional Sense: The Limits of Manual Validation

Manual penetration testing and red teaming remain valuable for uncovering complex attack paths and assessing detection and response capabilities. However, their purpose is strategic, not operational. Penetration tests are designed to validate assumptions in specific segments of the environment, while red teams simulate real-world adversaries to test resilience under stealth conditions.

Neither is built to support continuous, scalable vulnerability validation. 

They are time-bound, personnel-intensive, and inherently limited in coverage. More importantly, they do not provide systematic visibility into which vulnerabilities are truly exploitable across your entire environment on an ongoing basis. In a threat landscape where new CVEs are disclosed daily and environments change hourly, relying solely on episodic testing leaves significant exposure unmeasured.

Why Exploitability Validation Requires Continuous, Evidence-Based Testing

Exploitability is not static. 

As environments evolve, new assets are introduced, configurations change, and attackers adapt. A vulnerability that was blocked yesterday might become exploitable tomorrow due to a misconfiguration, expired control, or new attack vector.

Continuous, evidence-based testing addresses this by simulating and emulating real-world attack behaviors, mapped to frameworks like MITRE ATT&CK, against your live environment. These simulations test whether vulnerabilities can be exploited, whether existing defenses stop the attack, and how far an adversary could progress if they succeed.

This approach provides concrete answers:

• Is this vulnerability exploitable here and now?
• Are controls actively blocking or silently failing?
• What is the impact if exploitation occurs?

The result is a continuously updated, validated view of your true exposure. Hence, it replaces assumptions with measurable risk and guides smarter prioritization decisions.

What True Validation Looks Like

True validation is more than confirming the existence of a vulnerability. It’s about proving whether that vulnerability poses a real risk in your environment. By continuously simulating real-world attacks across your live systems, validation shows exactly which security vulnerabilities (a.k.a weaknesses) can be exploited, how far an attacker could progress, and whether your controls are effectively stopping threats in practice.

The result is a shift from reactive patching to confident, risk-based decision-making. 

Teams no longer waste time on theoretical risks. Instead, they focus on vulnerabilities that are validated as exploitable. More importantly, ignore those that are already neutralized or contained by existing defenses.

This precision drives measurable outcomes:

• Fewer rushed patches

• Reduced downtime and business disruption

• Improved SLA compliance and audit readiness

• Sharper prioritization and stronger security posture

Validation turns an overwhelming backlog of CVEs into a manageable set of proven risks—helping security teams do more with less, while reducing exposure and aligning security efforts with real business impact.

Conclusion: Stop Playing Whack-a-Mole with CVEs

Isn’t it the best-case scenario when your vulnerability scanner tells you that 60% of your findings are critical—only for exploitability validation to prove that just 1% of them actually pose real risk?

That’s the power of validation.

Picus Exposure Validation: Prioritize with Confidence Using Evidence-Based Validation

Instead of reacting to theoretical risk scores, you get evidence-based clarity. You reduce noise, conserve resources, and act only where it matters. Enter Picus Exposure Validation. A platform designed to continuously test your environment, measure the effectiveness of your controls, and surface the vulnerabilities that truly require action.

Because the flood vulnerability isn’t slowing down.

Traditional scoring systems provide breadth but lack precision. Security teams can’t afford to chase everything. And you shouldn’t have to.

The only way to reduce risk at scale is to validate continuously—transforming a static backlog into a focused, real-time risk reduction strategy.

👉 Picus Exposure Validation automates that shift—so you can prioritize with confidence, reduce false urgency, and focus your efforts where they’ll make the biggest impact.