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TuxCare BlogCVE and CVSS Explained: Your Essential Guide to Linux Security
by Rohan Timalsina
December 31, 2024 - TuxCare expert team
- CVE provides unique identifiers for vulnerabilities, facilitating tracking and communication across platforms.
- CVSS assigns numerical scores to vulnerabilities, helping prioritization based on severity.
- CVE and CVSS empower Linux administrators to effectively identify, assess, and mitigate risks.
From individual users to large organizations, the risk of cyberattacks is ever-present. To effectively mitigate these risks, it’s crucial to understand the fundamental concepts of CVE and CVSS scores.
CVE stands for Common Vulnerabilities and Exposures. In simple terms, it represents a publicly disclosed security vulnerability in a specific piece of software. Whereas, CVSS, or the Common Vulnerability Scoring System, is a standardized framework for assessing the severity of a vulnerability.
This article explores CVE and CVSS, explaining what they are and how they help in vulnerability management.
What Is a CVE?
A Common Vulnerability and Exposure (CVE) is a unique identifier assigned to publicly known software vulnerabilities. This naming system helps security researchers, vendors, and system administrators easily reference and track specific vulnerabilities. The CVE system originated at MITRE in 1999 with the launch of the CVE list containing just 321 records.
Fast forward to 2024, and more than 25,000 new vulnerabilities were disclosed in a single year – a staggering growth trajectory that highlights the critical role CVEs play in vulnerability management. Without a standardized system of identification, it becomes nearly impossible to distinguish and track them effectively. However, it’s important to note that not all vulnerabilities have CVEs assigned.
How Are CVEs Assigned?
CVEs are assigned by the CVE Numbering Authorities (CNAs), a group responsible for coordinating the assignment of unique identifiers to publicly known vulnerabilities. CNAs work closely with security researchers, vendors, and other stakeholders to identify and document vulnerabilities.
A CVE identifier is a unique text string in the format CVE-Year-Number. For example, CVE-2014-0160 refers to the infamous Heartbleed vulnerability. The “2014” indicates the year the CVE was made public, while “0160” is the unique number assigned to the vulnerability that year. These numbers are reset every year.
A CVE entry can be assigned but not disclosed immediately. This delay is often intentional, allowing the original vendor or software developer time to release a fix. By the time the CVE information is made public, the patch or mitigation is typically ready for deployment, reducing the risk to end-users.
What is CVSS?
The Common Vulnerability Scoring System (CVSS) is a standardized framework for assessing the severity of vulnerabilities. Managed by the Forum of Incident Response and Security Teams (FIRST), CVSS assigns a numerical score to a vulnerability, indicating its severity. This helps organizations prioritize vulnerabilities based on their CVSS scores and focus on addressing the most critical threats first.
The CVSS Scoring System
CVSS scores range from 0.0 to 10.0, with higher scores indicating more severe vulnerabilities. The CVSS scoring system evaluates vulnerabilities based on three key metric groups:
Base Score: This score represents the inherent properties of a vulnerability that are consistent over time and across environments. It includes factors like attack complexity, required privileges, user interaction, and potential impact.
Temporal Score: This score accounts for factors that can change over time, such as the patch availability, exploit code maturity, and report confidence metric.
Environmental Score: This score reflects the specific characteristics of the target environment, such as the presence of security controls, the value of affected assets, and the potential impact on organizational goals.
CVSS scores are used to categorize vulnerabilities into severity levels:
- 0.0: None
- 0.1 – 3.9: Low
- 4.0 – 6.9: Medium
- 7.0 – 8.9: High
- 9.0 – 10.0: Critical
These scores are often displayed alongside CVE entries in databases like the NVD, providing a quick snapshot of the risk level. The National Vulnerability Database (NVD) is a U.S. government-sponsored repository that provides detailed information on publicly known vulnerabilities. It includes descriptions of CVEs, their associated vulnerabilities, and potential exploits.
The Importance of CVSS Versions
The Common Vulnerability Scoring System (CVSS) has multiple versions, with the latest being CVSS 4.0. Unlike CVSS v2.0 and CVSS v3.x, it consists of four metric groups: Base, Threat, Environmental, and Supplemental. These versions have evolved over time to enhance the accuracy and consistency of vulnerability scoring. Therefore, the CVSS version used to assess the vulnerability can significantly impact the score assigned to a vulnerability.
For example, a vulnerability might receive a “High” severity rating under CVSS 3.0 but only a “Medium” rating under CVSS 2.0. For this reason, it’s important to specify the CVSS version whenever a score is mentioned, or else the score is impossible to interpret correctly.
Newer versions of CVSS aim to reduce subjectivity in scoring by refining the calculation methodology and introducing clearer guidelines. However, there can still be some degree of subjectivity in CVSS scoring. Security analysts may assign varying weights to the factors contributing to a CVSS score, which can lead to differences in the final score across CVE registries.
Why CVE and CVSS Matter for Linux Administrators
Linux operating systems are widely used in enterprise environments, making them attractive targets for attackers. For Linux administrators and security teams, CVE and CVSS play a crucial role in identifying and assessing vulnerabilities. By combining CVE IDs and CVSS scores, they can effectively prioritize and address the most critical vulnerabilities. This not only streamlines efficient vulnerability management but also simplifies adherence to regulatory and security standards.
However, even with CVE tracking and CVSS prioritization, one of the biggest challenges for Linux administrators is applying patches promptly without disrupting operations. Traditional patching methods often require system reboots, leading to downtime and service interruptions. Live patching addresses this challenge by enabling the deployment of kernel patches without rebooting the system.
TuxCare’s KernelCare Enterprise offers an automated live patching solution for Linux distributions that allows you to apply security updates immediately without requiring a reboot. By eliminating downtime, KernelCare significantly reduces the window of vulnerability exposure and addresses key operational concerns while enhancing security and compliance.
Final Thoughts
CVEs provide a standardized method to identify and track security risks, while CVSS offers a clear numerical rating to evaluate the severity of these vulnerabilities. The transparency and actionable insights offered by CVE and CVSS scores are invaluable in maintaining system security and compliance. By leveraging these frameworks with live patching tools like KernelCare Enterprise, organizations can effectively mitigate risks, enhance security, and ensure compliance with industry standards.
