sast-pathtraversal

sast-pathtraversal is a skill for Claude Code, Codex from utkusen/sast-skills. It costs 98 tokens per session (6,804 once invoked), scanned A, original, MIT.

A code-security check for path traversal, where input such as ../ may escape an intended folder and access other files.

In plain words
What is it for?
Use it to inspect file reads, writes, or downloads that build paths from user input. It requires a prior code-architecture analysis.
Why use it?
It helps find cases where user input reaches file operations without enough protection. It traces possible problems and combines the results into one report.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions subagents; installed under .agents/ (shared by several agents).

Needs its repository: it reads a path above its own folder, which exists only inside the repository. The line is - Using `os.path.join` alone without `realpath` — `os.path.join('/base', '../etc/passwd')` still produces `/etc/passwd`.

Good fit Use it to inspect file reads, writes, or downloads that build paths from user input. It requires a prior code-architecture analysis.

Compare 6 skills from other repositories ↓
About the project

SAST Skills is a collection of agent workflows that inspect web and mobile application code for security vulnerabilities, where SAST means static application security testing. Developers and security reviewers use it to map a codebase, verify possible flaws, and produce a severity-ranked remediation report. The catalogue entries are the project's vulnerability-detection and reporting skills.

utkusen/sast-skills · 1,309 stars · on GitHub

Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/utkusen/sast-skills
agentmods
npx agentmods add skills/utkusen/sast-skills/sast-pathtraversal

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for sast-pathtraversal

README.md
[![agentmods](https://agentmods.dev/badge/skills/utkusen/sast-skills/sast-pathtraversal/github.svg)](https://agentmods.dev/skills/utkusen/sast-skills/sast-pathtraversal)
Your own site
<a href="https://agentmods.dev/skills/utkusen/sast-skills/sast-pathtraversal"><img src="https://agentmods.dev/badge/skills/utkusen/sast-skills/sast-pathtraversal/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for sast-pathtraversal

Your own site · 80×15
<a href="https://agentmods.dev/skills/utkusen/sast-skills/sast-pathtraversal"><img src="https://agentmods.dev/badge/skills/utkusen/sast-skills/sast-pathtraversal.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 98 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 6,804 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 5 findings, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Privilege Escalation · line 23
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 438
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 440
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 465
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
  • high Privilege Escalation · line 538
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00098 $0.06804
Opus 5 $0.00049 $0.03402
Sonnet 5 $0.00020 $0.01361
Haiku 4.5 $0.00010 $0.00680

Measured 12d ago against content hash 1756514d03b3, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

sast-pathtraversal scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 12d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

> [curl command or payload to confirm; show traversal and encoded variants as appropriate]
sast-files/.agents/skills/sast-pathtraversal/SKILL.md · 545 lines

How it starts

The opening of the file, as written. The whole thing — 545 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Path Traversal Detection

You are performing a focused security assessment to find path traversal vulnerabilities in a codebase. This skill uses a three-phase approach with subagents: recon (find file-loading sinks with dynamic paths), batched verify (trace user input and check mitigations in parallel batches of 3), and merge (consolidate batch results into one report).

Prerequisites: sast/architecture.md must exist. Run the analysis skill first if it doesn't.


What is Path Traversal

Path traversal (also called directory traversal) occurs when user-supplied input is incorporated into a file path that is then used to read, write, or serve files from the filesystem — without properly constraining the resulting path to an intended base directory. An attacker can supply sequences like ../ or encoded variants (%2e%2e%2f, ..%2f, %2e%2e/) to escape the intended directory and access arbitrary files such as /etc/passwd, application source code, credentials, or private keys.

The core pattern: unvalidated user input reaches a filesystem operation and the resolved path is not verified to remain within the intended base directory.

What Path Traversal IS

  • Serving a user-requested filename directly from a base directory without canonicalizing and checking the resulting path: open(os.path.join(BASE_DIR, user_filename))
  • Constructing a file path from a URL parameter and passing it to a file-read function: fs.readFile(path.join(__dirname, req.query.file), ...)
  • Template rendering or include directives driven by user input: include($_GET['page'] . '.php')
  • Archive extraction (ZipFile, tarfile, zipslip) where entry names are used as output paths without stripping ../ components
  • Using send_file() / send_from_directory() / res.sendFile() with an unsanitized user-controlled path
  • Reading a file whose path is derived from a user-controlled database value that was stored without sanitization

What Path Traversal is NOT

Read the full file on GitHub · 545 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 12d ago First seen · 545 lines · 98 tokens per session scan A 1756514d03b3

Subscribe to this mod's changes

sast-pathtraversal is a skill published in the GitHub repository utkusen/sast-skills (1,309 stars, last pushed 5mo ago), licensed MIT. It adds 98 tokens to every session and 6,804 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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