Regex DoS

Resource Exhaustion Through Pattern Matching

What is Regex DoS? Regular Expression Denial of Service (Regex DoS) is an attack that exploits inefficient or poorly designed regular expressions in an application to cause excessive CPU or memory usage, often leading to service disruption.

How It Works: When a web application performs input validation using regular expressions, a malicious attacker can input specially crafted strings that trigger excessive backtracking, causing the regex engine to consume inordinate resources, resulting in denial of service.

Why It Matters: A poorly optimized regex can lead to a performance bottleneck, making it easy for attackers to overload a service, especially on applications that handle user-generated content or large amounts of data.

Common Use Cases: Regex DoS attacks are often exploited on web applications that use regular expressions to validate user input or parse complex data structures. Attackers aim to exhaust system resources, causing crashes or delays in response times.

By carefully designing and testing regular expressions, developers can minimize the risk of DoS attacks and improve the overall performance of their applications.