Refactor score method and add round_up function

[taladrane]

Proposed changes

Refactor score method to return float and add rounding functionality to align with https://www.first.org/cvss/v3-1/specification-document#Appendix-A---Floating-Point-Rounding .

Problem

The CVSS 3.1 implementation was missing the required roundup function specified in the CVSS 3.1 specification (Appendix A), causing certain vectors to produce incorrect scores.

Most notably, the vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H was returning a score of 10.0 instead of the correct 9.9.

Root Cause

The CVSS 3.1 specification requires a specific rounding function that rounds up to 1 decimal place using integer arithmetic to avoid floating-point precision issues. The current implementation was returning raw calculated values without applying this mandatory rounding step.

Solution

Implemented the round_up function following the CVSS 3.1 specification Appendix A:

• Multiplies input by 100,000 and rounds to nearest integer
• Uses integer arithmetic to avoid floating-point errors
• Rounds up to the next 0.1 unless already at a 0.1 boundary

Types of changes

What types of changes does your code introduce to CvssSuite?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR.

• Unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[0llirocks]

@taladrane thank you for your PR. The method you are adding already exists as a helper here. And that helper method is also called with each score for cvss31. Maybe you can find out the exact location where the helper is missing. Adding it only for base might fix your issue, but what about the other scores? Are they also affected and why does the helper does not work in cvss31.rb? I will take a closer look once I find time.

Best regards
Olli