Race Condition - TOCTOU Scanner
Tests for time-of-check to time-of-use race conditions.
What is Race Condition - TOCTOU?
Time-of-Check to Time-of-Use (TOCTOU) race conditions occur when a security check and the subsequent action on a resource happen at different times, allowing attackers to change the resource between the check and use. This creates a window where the validated state no longer reflects reality when the action occurs.
Why is This Important?
TOCTOU vulnerabilities enable privilege escalation, authentication bypass, and data manipulation. Attackers exploit the timing gap to swap authorized resources with unauthorized ones, bypass file permission checks, or manipulate validated data. These are particularly dangerous because they can bypass otherwise correct security logic.
How It Works
1. Attack Surface Mapping
Identifies complex attack vectors including race conditions, desync points, and logic flaws in your application.
2. Advanced Exploitation
Executes sophisticated attack techniques that bypass traditional security controls and detection mechanisms.
3. Impact Assessment
Demonstrates real-world impact with detailed exploitation chains and business risk analysis.
Key Capabilities
Expert-level security testing for sophisticated vulnerabilities that evade traditional scanning tools.
- Race condition and timing attack detection
- Request smuggling and desync analysis
- Business logic flaw identification
- Chained exploit development
- Protocol-level vulnerability testing
Frequently Asked Questions
How do TOCTOU attacks work practically?
Example: An app checks if a user owns file A, then reads file A. Attacker uses symbolic links to point 'A' to their file during check, then quickly switches it to point to /etc/passwd before read. The check passes (user owns their file), but the read accesses the password file.
Where are TOCTOU vulnerabilities commonly found?
Common locations: file operations (check permission then access), symbolic link handling, temporary file usage, privilege elevation flows, multi-step transactions, authentication followed by action, and any check-then-act pattern with shared resources.
How do you detect TOCTOU vulnerabilities?
Detection methods: code review for check-then-act patterns, static analysis tools, fuzzing with concurrent requests, symbolic link testing, testing with debugger-controlled timing, and parallel request testing with varying delays to find the race window.
How do I prevent TOCTOU race conditions?
Prevention: use atomic operations, open files and hold handles (don't re-open), use file descriptor operations instead of paths, implement proper locking, avoid symbolic links in security-critical paths, use transaction-based approaches, and design for concurrent access from the start.
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