# Inefficient Regular Expression Complexity (CWE-1333)

The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles.

**Stack:** Go

- Prevalence: Mittel 3 Sprachen abgedeckt
- Impact: Hoch 1 Regeln mit hohem Schweregrad
- Prevention: Dokumentiert 3 Fix-Beispiele

**OWASP:** Injection (A03:2021-Injection) - #3

## Description

Certain regular expression patterns can take exponential time to evaluate on certain inputs (ReDoS). Attackers can craft inputs that cause the regex engine to consume excessive CPU time, leading to denial of service.

## Prevention

Präventionsstrategien für ReDoS basierend auf 1 Shoulder-Erkennungsregeln.

### Go

Avoid nested quantifiers in regex; use specific character classes instead

## Consequences

- DoS

## Mitigations

- Verschachtelte Quantifizierer und überlappende Alternationen in Regex vermeiden
- Timeout-Mechanismen für Regex verwenden
- Den Einsatz nicht-backtrackender Regex-Engines erwägen

## Detection

- Total rules: 3
- Languages: go, javascript, typescript, python

## Rules by Language

### Go (1 rules)

- **Regular Expression Denial of Service** [MEDIUM]: Regex pattern with nested quantifiers causes catastrophic backtracking.
  - Remediation: Avoid nested quantifiers like (a+)+. Use possessive quantifiers or atomic groups.

```go
// Avoid patterns like: (a+)+, (.*)*
// Use specific patterns instead
re := regexp.MustCompile(`^[a-z]+$`)
```

Learn more: https://shoulder.dev/learn/go/cwe-1333/regex-dos