# Cwe 1333 Redos

> Use this skill when you need to remediate CWE-1333 (ReDoS (Regular Expression Denial of Service)) vulnerabilities in Java code. Triggers on SAST findings, security reviews, or when fixing redos (regular expression denial of service) issues.

- Skill: `developerscoffee/cwe-1333-redos` (Agent Skill)
- Install (CLI): `npx skillmds@latest add developerscoffee/cwe-1333-redos`
- Raw SKILL.md: https://api.skillmd.com/api/skills/developerscoffee/cwe-1333-redos/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Security
- License: MIT
- Author: DevelopersCoffee (https://skillmd.com/u/developerscoffee)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/developerscoffee/cwe-1333-redos

---


# CWE-1333 ReDoS (Regular Expression Denial of Service)

## Description

ReDoS (Regular Expression Denial of Service)

Reference:
https://cwe.mitre.org/data/definitions/1333.html


**OWASP Category**: A03:2021 – Injection


---

## Vulnerable Pattern


### ❌ Example 1: Vulnerable Pattern

```java
// VULNERABLE: Catastrophic backtracking
Pattern emailPattern = Pattern.compile("^([a-zA-Z0-9]+)+@[a-zA-Z0-9]+$");
Pattern nested = Pattern.compile("(a+)+b");  // Nested quantifiers

// User input matched against evil pattern
String userInput = request.getParameter("text");
if (userInput.matches("^(([a-z])+.)+[A-Z]([a-z])+$")) {
    // Process
}
```


**Why it's vulnerable:** This pattern is vulnerable to ReDoS (Regular Expression Denial of Service)




---

## Deterministic Fix


### ✅ Secure Implementation: Secure Implementation

```java
// SECURE: Use possessive quantifiers or atomic groups
// Option 1: Possessive quantifiers (no backtracking)
Pattern emailPattern = Pattern.compile("^[a-zA-Z0-9]++@[a-zA-Z0-9]++$");

// Option 2: Atomic groups
Pattern safePattern = Pattern.compile("^(?>[a-zA-Z0-9]+)@(?>[a-zA-Z0-9]+)$");

// Option 3: Timeout with interruptible matching
ExecutorService executor = Executors.newSingleThreadExecutor();
Future<Boolean> future = executor.submit(() ->
    pattern.matcher(userInput).matches()
);
try {
    boolean result = future.get(100, TimeUnit.MILLISECONDS);
} catch (TimeoutException e) {
    future.cancel(true);
    throw new IllegalArgumentException("Pattern match timeout");
}
```


**Why it's secure:** Implements proper protection against ReDoS (Regular Expression Denial of Service)




---

## Detection Pattern

Look for these patterns in your codebase:


```bash
# Find nested quantifier patterns
grep -rn "Pattern.compile" --include="*.java" | grep -E "\\+\\)\\+|\\*\\)\\*"
```



---

## Remediation Steps


1. Avoid nested quantifiers like (a+)+

2. Use possessive quantifiers (++) when possible

3. Implement timeout for regex matching

4. Validate input length before regex matching


---

## Key Imports

```java

import java.util.regex.Pattern;

import java.util.concurrent.ExecutorService;

```

---

## Verification

After remediation:


- Run SAST scanner to confirm vulnerability is resolved

- Review all instances of the vulnerable pattern

- Add unit tests that verify the secure implementation

- Check for similar patterns in related code


---

## Trigger Examples

```
Fix CWE-1333 vulnerability
Resolve ReDoS (Regular Expression Denial of Service) issue
Secure this Java code against redos (regular expression denial of service)
SAST reports CWE-1333
```

---

## Common Vulnerable Locations

| Layer | Files | Patterns |
|-------|-------|----------|

| Controller | `*Controller.java` | User input handling |

| Service | `*Service.java` | Business logic |

| Repository | `*Repository.java` | Data access |


---

## References


- [CWE-1333: ReDoS](https://cwe.mitre.org/data/definitions/1333.html)


---

**Source**: Generated by [Java CWE Security Skills Generator](https://github.com/DevelopersCoffee/java-cwe-security-skills)
**Last Updated**: 2026-03-07