Identifying and addressing vulnerabilities is critical to maintaining the security of software applications. With cyber threats constantly emerging, organizations must first prioritize which vulnerabilities to address. To do this effectively, they need a clear method for evaluating and managing these vulnerabilities. CVE scoring is crucial, as it helps organizations rank vulnerabilities based on their potential impact.
At the beginning of 2024, researchers discovered 612 new common IT security vulnerabilities and exposures (CVEs). This followed a record-breaking 29,000+ CVEs reported in 2023. These numbers highlight the growing urgency for effective CVE security measures to protect against escalating cyber threats.
What is CVE Scoring?
CVE stands for Common Vulnerabilities and Exposures, a list of publicly disclosed cybersecurity vulnerabilities and exposures. Each entry in the CVE list gets a unique identifier called a CVE ID, which specifically references a vulnerability. The MITRE Corporation manages this system, standardizing how vulnerabilities are identified and cataloged. This ensures everyone in cybersecurity uses the same reference when discussing specific threats.
CVE scoring involves evaluating each CVE entry and assigning a numerical score based on its severity. This score helps organizations determine the priority level for addressing the vulnerability.
It allows them to allocate resources effectively and mitigate potential risks. The scoring system evaluates factors like ease of exploitability. It also considers the impact on confidentiality, integrity, and availability (often referred to as the “CIA triad”). Additionally, it assesses the potential for remediation.
How NVD, the MITRE CVE List, and CVE Scoring Work Together
Understanding the connection between the National Vulnerability Database (NVD), the MITRE CVE List, and CVE scoring is essential for grasping how vulnerabilities are managed in the cybersecurity ecosystem.
The MITRE CVE List starts by identifying vulnerabilities and assigning them a CVE ID. However, this list provides only the basic information about each vulnerability. The NVD, operated by the National Institute of Standards and Technology (NIST), enriches this data by providing detailed descriptions, references, and most importantly, CVE scoring through the Common Vulnerability Scoring System (CVSS).
NVD is a key resource because it serves as a repository of standards-based vulnerability data, which helps organizations understand the impact of a vulnerability more comprehensively. NVD includes not only CVSS scores but also in-depth information such as:
- Detailed descriptions of each vulnerability, including technical details and the context in which the vulnerability could be exploited.
- Impact metrics that show how the vulnerability could affect different parts of an organization’s system.
- Remediation information such as links to patches, advisories, and mitigations.
Because of its comprehensive nature, the NVD is the go-to source for organizations when they need to assess the real-world impact of a vulnerability and understand how to address it effectively.
CVSS: The Most Used CVE Scoring System
The most widely used method for CVE scoring is the Common Vulnerability Scoring System (CVSS), maintained and developed by the Forum of Incident Response and Security Teams (FIRST). In addition, CVSS provides a standardized way of measuring the severity of vulnerabilities. This makes it easier for organizations to prioritize which ones to address first.
Specifically, CVSS scores vulnerabilities on a scale from 0 to 10. Here, 0 represents no risk and 10 represents the highest level of severity. Moreover, the scoring is based on four main metric groups:
Base Score:
This reflects the intrinsic characteristics of a vulnerability that are constant over time and across user environments. The base score considers factors like exploitability. This refers to how easy it is to exploit the vulnerability. It also evaluates the impact on confidentiality, integrity, and availability.
Temporal Score:
This adjusts the base score based on factors that change over time, like whether a fix is available or if an exploit is actively being used. Temporal metrics include exploit code maturity, remediation level, and report confidence.
Environmental Score:
This allows organizations to customize the CVSS score to reflect the impact of the vulnerability within their specific environment. It considers factors like the importance of the affected system and the potential collateral damage.
Supplemental Metric Group:
It is introduced in CVSS v4.0 and provides additional context that can influence the overall risk assessment. This includes considerations like safety requirements, automatable metrics (which measure how automation impacts exploitation), and unique characteristics that might not fit within the other metric groups. Although the overall CVSS score does not include these metrics, they offer valuable insights. As a result, they help organizations make more informed decisions about managing vulnerabilities.
The latest version, CVSS v4.0, introduces these enhancements to improve the accuracy and usability of vulnerability scoring. By refining the metrics, CVSS v4.0 captures the complexity and context of vulnerabilities more effectively. This ensures that the scores provide a more precise reflection of the actual risk.
Real-World Example: CVE-2021-44228 (Log4Shell)
To illustrate how CVE scoring works in practice, let’s look at CVE-2021-44228, commonly known as Log4Shell. This Apache Log4j 2 library vulnerability allows for remote code execution (RCE). As a result, an attacker could take control of an affected system.
- CVE ID: CVE-2021-44228
- CVSS Base Score: 10.0 (Critical)
- Attack Vector: Network (N) – Exploitable remotely.
- Attack Complexity: Low (L) – Straightforward to exploit.
- Privileges Required: None (N) – No privileges needed.
- User Interaction: None (N) – No user interaction is required.
- Scope: Changed (C) – Affects resources beyond its original scope.
- Confidentiality, Integrity, Availability Impact: High (H) – Complete compromise of confidentiality, integrity, and availability.
NVD provided a CVSS score of 10.0, indicating the highest level of severity. The widespread nature of this vulnerability, combined with the ease of exploitation, made it a top priority for remediation across the globe.
Challenges in CVE Scoring: Limitations and Implications
While the Common Vulnerabilities and Exposures (CVE) system offers a standardized way to identify and track vulnerabilities, several limitations affect its effectiveness in managing risks.
CVE-2021-44228 (Log4Shell) illustrates these challenges:
- Limited Detail on Exploitation: CVE-2021-44228 provides a unique identifier but lacks comprehensive details on how attackers might exploit it. Although experts consider it critical, the CVE entry does not fully explain the exact methods attackers use or the specific configurations that increase vulnerability. This gap leaves organizations uncertain about the real-world risk.
- Variability in Reporting: CVE records vary widely in content and quality. Some, like CVE-2021-44228, offer detailed descriptions and technical information, while others remain brief or incomplete. This inconsistency challenges organizations when they try to assess a vulnerability’s risk based solely on its CVE entry.
- Lack of Contextual Relevance: CVE entries use a standardized format that might not reflect the specific context of different environments. For instance, CVE-2021-44228 impacts systems differently depending on a company’s infrastructure. This misalignment leads to inaccurate risk assessments if the CVE details don’t match the specific environment.
- Delay in Disclosure: There’s often a lag between discovering a vulnerability and adding it to the CVE database. During this gap, attackers might exploit vulnerabilities like CVE-2021-44228 before they become public, increasing the risk due to delays in awareness and remediation.
- Focus on Known Vulnerabilities: CVE entries cover only publicly disclosed vulnerabilities, which leaves zero-day vulnerabilities and undisclosed threats unaccounted for. Relying solely on CVE exposes organizations to emerging risks that the database has not yet cataloged.
- Inconsistent Quality of Entries: The quality of CVE entries varies depending on the source. Some, like CVE-2021-44228, receive regular updates with new details, while others remain static, leading to inconsistencies and potential gaps in data.
EPSS: Enhancing CVE Security for Comprehensive Vulnerability Management
CVE-2021-44228 also highlights where the Common Vulnerability Scoring System (CVSS), while robust, falls short. This shortcoming underscores the importance of the Exploit Prediction Scoring System (EPSS).
What is EPSS?
EPSS uses a data-driven framework to predict the likelihood of exploitation for vulnerabilities like CVE-2021-44228 within the next 30 days. Unlike CVSS, which measures potential impact, EPSS estimates the probability of exploitation based on historical data and trends.
Why EPSS Matters
- Enhanced Prioritization: EPSS enables organizations to prioritize vulnerabilities based not just on severity but also on the likelihood of exploitation. For example, when security teams know that CVE-2021-44228 has a high probability of exploitation, they focus remediation efforts where they need it most.
- Proactive Defense: EPSS allows security teams to take preemptive actions against likely-to-be-exploited vulnerabilities, reducing the risk of successful attacks.
- Contextual Decision-Making: EPSS provides additional context that CVSS alone might miss, such as identifying vulnerabilities actively targeted by attackers. This leads to more informed and strategic decision-making.
- Resource Optimization: For organizations with limited resources, EPSS helps efficiently allocate efforts to vulnerabilities that pose the greatest threat, ensuring a more effective defense strategy.
Limitations of EPSS
Despite its advantages, EPSS has limitations. It relies on historical data, which might not always reflect the current threat landscape. Its short-term focus on predicting exploitation within 30 days may overlook long-term threats.
EPSS provides general insights without accounting for the specific context of individual environments. Finally, it depends on past exploitation patterns, which might not capture rapid changes in attack techniques or newly discovered vulnerabilities.
Balancing CVE and EPSS for Optimal Vulnerability Management
To manage vulnerabilities effectively, organizations must understand and address the limitations of both CVSS and EPSS. Integrating these tools gives a more comprehensive view of the vulnerability landscape. This approach balances severity with the likelihood of exploitation, leading to better prioritization, informed decision-making, and improved cybersecurity outcomes.
Tackles the Challenge of Prioritizing Critical Vulnerabilities
Throughout this blog, we’ve explored the intricacies of CVE scoring, the crucial role of the National Vulnerability Database (NVD), and how tools like the Exploit Prediction Scoring System (EPSS) add depth to vulnerability management by predicting the likelihood of exploitation. However, managing vulnerabilities effectively requires more than just understanding these concepts—it demands a comprehensive approach that adapts to your organization’s specific security needs.
Out of approximately 176,000 known vulnerabilities, over 19,000 carry a CVSS score of 9.0–10.0, signifying critical risks. Yet, the majority—about 77.5%—fall within a mid-range score of 4.0 to 8.0. This wide distribution highlights the challenge: of prioritizing which vulnerabilities to address first and how to do so with limited resources while maintaining a robust defense.
Xygeni’s Software Composition Analysis (SCA) solution addresses this challenge by integrating CVE scoring with EPSS and other contextual tools, giving you a complete picture of your vulnerability landscape. Our solution thoroughly scans your codebase across multiple sources, including NPM, GitHub, and OWD, ensuring you don’t miss any potential security threats.
How Xygeni’s SCA Solution Complements Your Vulnerability Management Strategy:
CVE Scoring and EPSS Integration: As discussed earlier, combining traditional CVE scoring with EPSS enables a more nuanced understanding of risk. By knowing, for example, that CVE-2021-44228 has a high probability of exploitation, your security team can prioritize addressing it before less pressing vulnerabilities, optimizing your efforts.
Advanced Reachability Analysis: Xygeni’s solution doesn’t stop at identification; it assesses whether vulnerabilities can be exploited within your specific environment. This helps you focus on the vulnerabilities that matter most, ensuring your resources are used effectively to mitigate real threats.
Comprehensive Contextual Awareness: Building on the idea that no single tool provides a complete picture, Xygeni integrates multiple advisory sources and scoring systems. This approach allows you to adapt vulnerability management strategies to fit your organization’s unique context, ensuring that you are not only aware of potential threats but are also equipped to address them appropriately.
Continuous Monitoring and Real-Time Alerts: Given the constant evolution of cyber threats, Xygeni offers continuous monitoring and real-time alerts to ensure that your software remains secure against newly emerging vulnerabilities. This ongoing vigilance is critical in maintaining a strong security posture.
By integrating these features, Xygeni’s SCA solution empowers your organization to manage vulnerabilities effectively, helping you build a tailored approach that aligns with your specific security needs. With Xygeni, you gain the ability to prioritize and address the most critical threats, ensuring your software remains resilient in an ever-changing threat landscape.
Take the next step in optimizing your vulnerability management. Request a Demo Today to see how Xygeni can help you create a more secure and adaptable cybersecurity strategy.
