pentest-race-conditions

pentest-race-conditions is a skill for Claude Code, Codex from jd-opensource/JoySafeter. It costs 26 tokens per session (536 once invoked), scanned A, original, Apache-2.0.

A security test for race conditions, where simultaneous actions are handled incorrectly. TOCTOU means “time of check to time of use,” when a value changes between validation and use.

In plain words
What is it for?
Use it to test transfers, coupons, purchases, voting, token creation, and file operations with parallel requests and multiple authorized sessions.
Why use it?
It helps find bugs that can cause duplicate transactions, double spending, quota or limit bypasses, and unauthorized changes.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to test transfers, coupons, purchases, voting, token creation, and file operations with parallel requests and multiple authorized sessions.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/jd-opensource/joysafeter/pentest-race-conditions
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add jd-opensource/JoySafeter --skill pentest-race-conditions
Clone the repo
git clone --depth 1 https://github.com/jd-opensource/JoySafeter

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 pentest-race-conditions

README.md
[![agentmods](https://agentmods.dev/badge/skills/jd-opensource/joysafeter/pentest-race-conditions/github.svg)](https://agentmods.dev/skills/jd-opensource/joysafeter/pentest-race-conditions)
Your own site
<a href="https://agentmods.dev/skills/jd-opensource/joysafeter/pentest-race-conditions"><img src="https://agentmods.dev/badge/skills/jd-opensource/joysafeter/pentest-race-conditions/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 pentest-race-conditions

Your own site · 80×15
<a href="https://agentmods.dev/skills/jd-opensource/joysafeter/pentest-race-conditions"><img src="https://agentmods.dev/badge/skills/jd-opensource/joysafeter/pentest-race-conditions.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 26 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 536 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 pass 7 Sept 2026
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 $0.00026 $0.00536
Opus 5 $0.00013 $0.00268
Sonnet 5 $0.00005 $0.00107
Haiku 4.5 $0.00003 $0.00054

Measured 11d ago against content hash 351b26386da5, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

pentest-race-conditions 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 11d 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.

| Shell Concurrency | GNU parallel, xargs, curl | Quick parallel request testing |
skills/pentest-race-conditions/SKILL.md · 47 lines

How it starts

The opening of the file, as written. The whole thing — 47 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Pentest Race Conditions

Purpose

Exploit applications that fail to handle concurrent requests atomically — enabling double-spend, limit bypass, privilege escalation through parallel requests. Absent from standard WSTG categories but critical in real-world assessments.

Prerequisites

Authorization Requirements

  • Written authorization with explicit scope for concurrency testing
  • Test accounts with balances, quotas, or limited-use resources
  • Rollback plan for financial or state-mutating operations
  • Rate limit awareness — confirm acceptable burst volume with target owner

Environment Setup

  • Burp Suite Professional with Turbo Intruder extension
  • Python 3.x with asyncio/aiohttp for parallel request scripting
  • GNU parallel or xargs for shell-based concurrency
  • Multiple authenticated sessions (separate cookies/tokens)

Core Workflow

  1. Target Identification: Identify race-prone operations — balance transfers, coupon redemption, inventory purchase, vote/like systems, token generation, file operations.
  2. Single-Endpoint Races: Send N identical requests simultaneously to bypass "one per user" limits, duplicate transactions (limit-overrun).
  3. Multi-Endpoint TOCTOU: Exploit time gap between check and use — validate coupon then apply coupon, check balance then debit.
  4. Session-Level Races: Parallel password change + session refresh, simultaneous role change + action execution.
  5. Database-Level Races: Exploit missing row-level locks, test optimistic vs pessimistic concurrency, trigger deadlocks.
  6. Timing Synchronization: Use single-packet attack technique (Turbo Intruder) to synchronize requests within microseconds.
  7. Impact Documentation: Document financial/operational impact with precise reproduction steps and timing requirements.

Tool Categories

Category Tools Purpose
Timing Attacks Turbo Intruder, race-the-web Microsecond-synchronized parallel requests
Async Scripting Python asyncio/aiohttp, httpx Custom race condition scripts
Shell Concurrency GNU parallel, xargs, curl Quick parallel request testing
Proxy Analysis Burp Suite Repeater Request replay and timing observation
Database Monitoring pg_stat_activity, SHOW PROCESSLIST Observe lock contention and deadlocks

Read the full file on GitHub · 47 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 11d ago First seen · 47 lines · 26 tokens per session scan A 351b26386da5

Subscribe to this mod's changes

pentest-race-conditions is a skill published in the GitHub repository jd-opensource/JoySafeter (307 stars, last pushed yesterday), licensed Apache-2.0. It adds 26 tokens to every session and 536 once invoked, about $0.0001 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.