The Ever-Challenging Dilemma: Prioritizing Patches in the Era of CVSS 4.0

The Challenges and Promises of CVSS 4.0: A Step Forward for Vulnerability Management

Introduction

The upcoming release of Version 4.0 of the Common Vulnerability Scoring System (CVSS) is creating anticipation among security experts. Boasting improvements in the severity metric for security bugs, CVSS 4.0 aims to provide a more descriptive and accurate assessment of vulnerabilities. However, vulnerability experts caution that while CVSS 4.0 brings advancements, prioritizing patches and measuring exploitability will still present challenges.

The Evolution of CVSS

CVSS has been a widely used framework for assessing and communicating the severity of security vulnerabilities. The Forum of Incident Response and Security Teams (FIRST) recently offered a preview of the next version of CVSS at its annual conference. In version 4.0, the “temporal” metric will be replaced by the more detailed “threat” metric, offering better insight into the potential risks posed by a vulnerability.

Furthermore, CVSS 4.0 introduces two new factors for calculating the base metric: Attack Requirements (AT) and User Interaction (UI). These factors measure the complexity of an attack and whether user interaction is required. Additionally, the environmental score, a company-specific component of CVSS, gauges the impact a vulnerability can have on an organization’s IT environment.

Enhancements and Usability

FIRST contends that CVSS 4.0 enhances the overall usability of the scoring system. They encourage companies and organizations to try the metric to grade current vulnerabilities and provide feedback prior to the general release. The modifications introduced in CVSS 4.0 are viewed as a significant step forward since they incorporate capabilities crucial for teams that rely on threat intelligence and environmental metrics for accurate scoring.

Addressing Patch Prioritization

While a better version of CVSS could offer companies a more effective approach to determining which vulnerabilities should receive priority for patching, experts caution against treating it as a panacea. Various tools, such as CVSS, the Known Exploited Vulnerability (KEV) list from the US Cybersecurity and Infrastructure Security Agency (CISA), and proprietary systems like the Exploit Prediction Scoring System (EPSS) and the Coalition Exploit Scoring System, can assist in prioritizing patches.

Sasha Romanosky, a senior policy researcher at RAND Corp. and a contributor to CVSS and EPSS, emphasizes that the effectiveness of the prioritization approach depends on matching an organization’s capabilities and resources. Finding the strategy that produces the best, prioritized list for an organization is more crucial than which approach is used.

Strategies for Effective Prioritization

Dustin Childs, head of threat awareness for Trend Micro’s Zero Day Initiative (ZDI), emphasizes the importance of knowing an organization’s attack surface area. Conducting thorough asset discovery and understanding which systems are critical to the business are key to prioritization efforts. By recognizing the most essential systems, organizations can better allocate resources and patch vulnerabilities that pose the greatest risk.

Timing and Complexity Challenges

Despite the improvements introduced in CVSS 4.0, challenges persist regarding actionable assessments for prioritization. Scott Walsh, a senior security researcher at Coalition, highlights the need for quick generation of exploitability metrics. Delayed scoring of new vulnerabilities can leave organizations uncertain about which threats pose the highest potential risk to their digital ecosystems and technologies. Swift availability of guidance on severity and exploitability is crucial for organizations to make informed decisions regarding patch prioritization.

Another hurdle lies in the complexity of CVSS 4.0. With nearly 24 attributes used to calculate the base metric, security teams might face difficulties in comprehending their risk exposure. The evaluation process can become slow and cumbersome, impacting the timeliness of responses to emerging threats. Assessing the impact and requirements of these variables would require coordination among multiple business units.

Final Thoughts

CVSS 4.0 represents a notable advancement in vulnerability management, addressing shortcomings of its predecessor by providing a more descriptive and refined scoring methodology. However, challenges related to patch prioritization and measuring exploitability persist. Emphasizing the importance of tailoring the approach to an organization’s capabilities and resources, security experts have stressed the need for comprehensive asset discovery and swift availability of exploitability metrics. While CVSS 4.0 offers enhancements, organizations must be mindful of its complexities and limitations. Employing a multi-faceted strategy that considers various scoring systems and factors can ultimately lead to more effective and efficient vulnerability management.