Race Condition Hackviser May 2026

Create a dummy file that we own to pass the permission check.

user@hackviser:~$ touch /tmp/dummy
user@hackviser:~$ ln -s /tmp/dummy /tmp/link

In cybersecurity, a race condition occurs when a system’s behavior depends on the sequence or timing of uncontrollable events. If two threads or processes access a shared resource (like a file or memory) without proper locking, an attacker can slip in between the cracks. race condition hackviser

The classic example: Check-Then-Act.

But what if an attacker can create a symbolic link between the "Check" and the "Act" steps? Create a dummy file that we own to pass the permission check

Hackviser is an interactive platform for learning ethical hacking, pentesting, and CTF challenges. The Race Condition challenge falls under the concurrency vulnerabilities category, focusing on exploiting improper synchronization in a web application or system process. In cybersecurity, a race condition occurs when a

Difficulty level: Intermediate
Prerequisites: Basic understanding of multithreading, HTTP requests, file operations, or database transactions.

This challenge demonstrates the classic TOCTOU vulnerability. Even though the binary checked permissions, the check was decoupled from the usage, allowing an attacker to change the context (the symlink target) during the execution window.