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Miscalculation of CVSS 3.1 score vs. NVD/FIRST CVSS calculator

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#7,119 1 comment 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
45/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Domain
security

Research direction

Reproduce the discrepancy using the GitHub Advisories API endpoint for GHSA-vfww-5hm6-hx2j and the vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H. Compare the implementation's result with the NVD/FIRST calculators, then verify that this vector produces 9.6 and that related CVSS calculations remain correct.

Written by the indexing model from the issue text.

Description

The calculation of CVSS 3.1 score does not produce the same result as the NVD/FIRST CVSS calculator

For example, querying the CVSS score of GHSA-vfww-5hm6-hx2j / CVE-2025-55754 -

curl -L \
  -H "Accept: application/vnd.github+json" \
  -H "X-GitHub-Api-Version: 2022-11-28" \
  https://api.github.com/advisories/GHSA-vfww-5hm6-hx2j

Produces the vector and a score of 9.7 -

...
"cvss": {
    "vector_string": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H",
    "score": 9.7
  },
...

However, the same CVSS vector in both NVD and FIRST CVSS 3.1 calculators, produces a score of 9.6 -
https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H&version=3.1

Image

The expected outcome is that the calculation of the above vector will be equal to the NVD/FIRST calculation (9.6)

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