Race Condition Hackviser [work] Jun 2026

app.post('/redeem', async (req, res) => let points = await db.get(`points:$req.user.id`); if (points >= req.body.cost) await db.decrBy(`points:$req.user.id`, req.body.cost); await grantReward(req.user.id);

user@hackviser:~$ /opt/vuln_binary

: The OWASP community recommends "locking" Alex's account row the moment Request A starts, forcing Request B to wait in line until Request A is completely finished and the balance is zero. race condition hackviser

Race conditions are highly prized by bug bounty hunters because they target core business logic. Traditional automated scanners often miss them because they require precise timing and contextual understanding. 1. Financial and Gift Card Exploits

While specific walkthroughs for the "Hackviser Race Condition" lab are highly sought after by those climbing the platform's Hall of Fame 2. File Upload Overwrites Mathematically

user@hackviser:~$ ls -la /opt/vuln_binary -rwsr-sr-x 1 root root 16784 Jan 1 12:00 /opt/vuln_binary

Attackers target digital wallets, coupon code applications, or gift card redemption systems. By sending dozens of concurrent redemption requests, they can bypass balance limitations, redeeming a single-use coupon multiple times or withdrawing more funds than their account actually holds. 2. File Upload Overwrites coupon code applications

Mathematically, if each attempt wins with probability ( p = \frac\delta_\textattack\Delta t ), then after ( k ) attempts:

| Mitigation | Bypass via Hackviser | |------------|----------------------| | | Use /proc/self/fd symlink attack to bypass lock scope | | Atomic operations (CAS) | Race after CAS but before commit (e.g., double-fetch) | | Transaction isolation (SERIALIZABLE) | Use read-only race + out-of-band channel (cache side-channel) | | Deterministic scheduling (TSO) | Introduce async signals or page faults to deschedule victim |