# 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: Moyenne 3 langages couverts
- Impact: Élevé 1 règles de sévérité élevée
- Prevention: Documentée 3 exemples de correctifs

**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

Stratégies de prévention pour ReDoS basées sur 1 règles de détection Shoulder.

### Go

Avoid nested quantifiers in regex; use specific character classes instead

## Consequences

- DoS

## Mitigations

- Évitez les quantificateurs imbriqués et les alternances chevauchantes dans les regex
- Utilisez des mécanismes de timeout pour les regex
- Envisagez d'utiliser des moteurs de regex sans retour arrière (non-backtracking)

## 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