NVD - CVSS v3.1 Equations

CVSS v3.1 Equations

The CVSS v3.1 equations are defined below.

Base

The Base Score is a function of the Impact and Exploitability sub score equations. Where the Base score is defined as,

If (Impact sub score <= 0) 0 else,
Scope Unchanged₄ Roundup(Minimum[(Impact + Exploitability), 10])
Scope Changed Roundup(Minimum[1.08 × (Impact + Exploitability), 10])

and the Impact sub score (ISC) is defined as,

Scope Unchanged 6.42 × ISC_Base
Scope Changed 7.52 × [ISC_Base − 0.029] − 3.25 × [ISC_Base − 0.02]¹⁵

Where,

ISC_Base = 1 − [(1 − Impact_Conf) × (1 − Impact_Integ) × (1 − Impact_Avail)]

And the Exploitability sub score is,

8.22 × AttackVector × AttackComplexity × PrivilegeRequired × UserInteraction

Temporal

The Temporal score is defined as,

Roundup(BaseScore × ExploitCodeMaturity × RemediationLevel × ReportConfidence)

Environmental

The environmental score is defined as,

If (Modified Impact Sub score <= 0) 0 else,

If Modified Scope is Unchanged Round up(Round up (Minimum [ (M.Impact + M.Exploitability) ,10]) × Exploit Code Maturity × Remediation Level × Report Confidence)

If Modified Scope is Changed Round up(Round up (Minimum [1.08 × (M.Impact + M.Exploitability) ,10]) × Exploit Code Maturity × Remediation Level × Report Confidence)

And the modified Impact sub score is defined as,

If Modified Scope is Unchanged 6.42 × [ISC_Modified]

If Modified Scope is Changed 7.52 × [ISC_Modified − 0.029]-3.25× [ISC_Modified × 0.9731 − 0.02] 13

Where,
ISC_Modified = Minimum [[1 − (1 − M. IConf × CR) × (1 − M. IInteg × IR) × (1 − M. IAvail × AR)], 0.915]

The Modified Exploitability sub score is,

8.22 × M. AttackVector × M. AttackComplexity × M. PrivilegeRequired × M. UserInteraction

4 Where “Round up” is defined as the smallest number, specified to one decimal place, that is equal to or higher than its input. For example, Round up (4.02) is 4.1; and Round up (4.00) is 4.0.