Vulnerability Severity Level

FortiGuard IPS Event Name's Severity Level is mainly based on the ratings set forth by the Common Vulnerability Scoring System (CVSS). The CVSS is a vendor-neutral, industry standard that provides an open framework for communicating the characteristics and impacts of IT vulnerabilities.

FortiGuard Severity Level CVSS v2 Rating
Critical 9 - 10
High 7 - 8.9
Medium 4 - 6.9
Low 0.1 - 3.9
Info 0

Exceptions

  • If there is no CVSS rating posted, then the CVSS rating is calculated. A Base Score tool form is available at: http://nvd.nist.gov/cvss.cfm
  • If the vulnerable software/system is not common in a business network environment and the FortiGuard Severity Level would normally be Critical, then the FortiGuard Severity Level may be reduced to High.
  • If the vulnerability is a Denial of Service (DoS) attack and only affecting the availability of a remote service or host, then the FortiGuard Severity Level is adjusted to at most Medium for Client-side DoS and High for Server-side DoS
  • For any "remote code execution" type of vulnerability, the FortiGuard Severity Level is set to either High or Critical.
  • For identifying or detecting network traffic, the FortiGuard Severity Level is set to Informational.
  • For a vulnerability/exploit that is highly active, the FortiGuard Severity Level is temporarily set to either High or Critical. Later, the level may be reduced back to its normal level; generally this is based on the temporal parameter of a vulnerability.
  • For zero-day vulnerabilities where the rating has not yet been fully evaluated, the FortiGuard Severity Level is generally set at either Medium or High.
For more information on CVSS, visit A Complete Guide to the Common Vulnerability Scoring System Version 2.0.

Common Vulnerability Scoring System Version 2.0

The Common Vulnerability Scoring System (CVSS) provides an open framework for communicating the characteristics and impacts of IT vulnerabilities. CVSS consists of 3 groups: Base, Temporal and Environmental. Each group produces a numeric score ranging from 0 to 10, and a Vector, a compressed textual representation that reflects the values used to derive the score. The Base group represents the intrinsic qualities of a vulnerability. The Temporal group reflects the characteristics of a vulnerability that change over time. The Environmental group represents the characteristics of a vulnerability that are unique to any user's environment. CVSS enables IT managers, vulnerability bulletin providers, security vendors, application vendors and researchers to all benefit by adopting this common language of scoring IT vulnerabilities.