# Cvss Scorer

> Computes an exact CVSS v3.1 base score and vector from a vulnerability description infers metrics from context, asks one sharp question only when ambiguity would change the severity level. Trigger when the user needs a CVSS score for a vulnerability finding, is writing a bug bounty report or pentest finding needing a severity vector, says "score this" or "what's the CVSS?", or has a vulnerability…

- **Type:** Skill
- **Install:** `agentstack add skill-rifteo-skills-cvss-scorer`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [Rifteo](https://agentstack.voostack.com/s/rifteo)
- **Installs:** 0
- **Category:** [Data & Analytics](https://agentstack.voostack.com/c/data-and-analytics)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [Rifteo](https://github.com/Rifteo)
- **Source:** https://github.com/Rifteo/skills/tree/main/cvss-scorer

## Install

```sh
agentstack add skill-rifteo-skills-cvss-scorer
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# CVSS Scorer

Produce an exact CVSS v3.1 vector and score from a vulnerability description. Be decisive. Be accurate. Be short.

---

## When NOT to use

Do NOT produce a CVSS vector — respond normally — when:
- The user is asking what CVSS is or how it works (answer the theory question directly)
- The user wants a full risk assessment beyond CVSS — likelihood, business impact, SLAs (use `risk-assessor` instead)
- The user is asking how to fix a vulnerability (use `remediation-planner` instead)
- No specific vulnerability has been described — a score requires a concrete finding, not a hypothetical

---

## Core Behavior

- **Infer aggressively from context.** Most metrics can be determined from a good description. Do it.
- **Pick the best score when you have enough.** Do not flood with scenarios for every metric. Only surface ambiguity when it would change the severity bucket (e.g. Medium vs High) or meaningfully changes the score (≥1.0 difference).
- **Ask once, ask sharp.** If you need clarification, ask one short question, show 2–3 short conditional scores, then stop.
- **No metric-by-metric explanations.** Only explain a metric if it's non-obvious or the auditor asks. Never explain what AV, AC, PR, etc. mean unless asked.
- **No formula display.** The auditor does not need to see the math.
- **Do not assume AV:N by default.** Infer it. If the description says nothing about how the vuln is reached, ask — or state the assumption explicitly in one word.

---

## Metric Inference

### Attack Vector (AV)
- Web app, API, internet/intranet-reachable → **N**
- Same LAN / WiFi / Bluetooth required → **A**
- Local OS session required → **L**
- Physical device access required → **P**
- If not mentioned and not obvious → state "assumed AV:N (web app)" and flag it

### Attack Complexity (AC)
- IDOR with numeric/sequential ID → **L**
- IDOR with UUID/GUID → **H**
- Race condition → **H**
- MitM required → **H**
- Everything else standard → **L**

### Privileges Required (PR)
- Pre-auth / unauthenticated → **N**
- Any valid account → **L**
- Admin / elevated → **H**
- If unclear → ask (this is the most common ambiguity and always matters)

### User Interaction (UI)
- Stored XSS → **N**
- Reflected XSS, DOM XSS via URL → **R**
- CSRF, clickjacking → **R**
- Direct server-side vuln (SQLi, SSRF, RCE, IDOR, path traversal, XXE) → **N**
- File must be opened → **R**

### Scope (S)
- XSS (any type) → **C** (JS in victim browser = different security origin)
- SSRF → **C**
- XXE with SSRF → **C**
- SSTI / RCE → **C**
- LFI → RCE via log poison → **C**
- SQL injection, IDOR, path traversal, auth bypass, CSRF → **U**
- LFI (read only) → **U**
- Open redirect → **U**

### Confidentiality / Integrity / Availability
- Full read of sensitive data (PII, creds, tokens, secrets) → **C:H**
- Limited or indirect read → **C:L**
- No data exposure → **C:N**
- Write / modify / delete critical data or code execution → **I:H**
- Limited non-critical write → **I:L**
- Full DoS / crash / resource exhaustion → **A:H**
- Partial disruption → **A:L**
- Blind variants (blind SQLi, blind SSRF, blind XXE) → **C:L** not C:H (data inferred, not read)

---

## When to Ask

Only ask when the answer changes the severity bucket or the score by ≥1.0. Format: one question + 2–3 short conditional lines.

**Example — XSS impact unclear:**

> Can this XSS access the session cookie / lead to account takeover, or is HttpOnly set?
>
> - ATO possible (C:H/I:L): `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N` — **8.7 High**
> - No cookie, limited impact (C:L/I:L): `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N` — **5.4 Medium**

**Example — auth state unclear:**

> Is this endpoint pre-auth or does it require a valid session?
>
> - Pre-auth (PR:N): `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N` — **9.1 Critical**
> - Any user (PR:L): `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N` — **8.1 High**

If the auditor cannot answer, pick the most **technically accurate** option given available context — lean toward what the description implies, not the worst case.

---

## Output Format

```
CVSS:3.1/AV:_/AC:_/PR:_/UI:_/S:_/C:_/I:_/A:_
Score: X.X — Severity
```

Add a short note **only** for metrics that are non-obvious, were assumed, or could surprise the auditor. Skip the rest.

**Example output:**

```
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
Score: 4.3 — Medium
```
> AC:H — UUID-based IDOR, not enumerable. If the app exposes the UUID somewhere accessible to the attacker, revert to AC:L → 6.5 Medium.

---

## Common Patterns (internal reference — do not dump to output)

| Vulnerability | Typical Vector | Score |
|---|---|---|
| Unauth RCE (web) | AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H | 10.0 Critical |
| Auth RCE any user | AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H | 9.9 Critical |
| SQLi full dump pre-auth | AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N | 9.1 Critical |
| SQLi full dump low-priv | AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N | 8.8 High |
| IDOR numeric pre-auth PII | AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N | 7.5 High |
| IDOR UUID pre-auth PII | AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N | 5.9 Medium |
| IDOR numeric low-priv PII | AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N | 6.5 Medium |
| IDOR UUID low-priv PII | AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N | 4.3 Medium |
| Stored XSS → ATO | AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N | 8.7 High |
| Stored XSS no ATO | AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N | 5.4 Medium |
| Reflected XSS | AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N | 6.1 Medium |
| SSRF internal creds | AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N | 8.6 High |
| SSRF blind | AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N | 5.8 Medium |
| CSRF state change | AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N | 6.5 Medium |
| Path traversal read | AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N | 7.5 High |
| XXE file read | AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N | 7.5 High |
| XXE + SSRF | AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N | 8.6 High |
| SSTI → RCE pre-auth | AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H | 10.0 Critical |
| JWT alg:none / weak secret | AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N | 9.1 Critical |
| Open redirect | AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N | 4.3 Medium |
| Insecure deserialization RCE | AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H | 9.0 Critical |
| Account takeover broken auth | AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N | 9.1 Critical |

---

## Rules

- Self-XSS is not a valid standalone finding — flag it, do not score unless it chains
- For chained vulns: use the entry point's AV/AC/PR/UI and the final step's C/I/A/S
- When scope is Changed, use S:C weights for PR in the formula
- Blind variants (blind SQLi, blind SSRF, blind XXE) → C:L not C:H
- Never explain what CVSS metrics mean unless asked
- Never show the score formula or intermediate math in the output

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [Rifteo](https://github.com/Rifteo)
- **Source:** [Rifteo/skills](https://github.com/Rifteo/skills)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-rifteo-skills-cvss-scorer
- Seller: https://agentstack.voostack.com/s/rifteo
- Browse the marketplace: https://agentstack.voostack.com/browse

---
Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.