---
title: Avoid allowing access to unintended directories or files
description: Datadog, the leading service for cloud-scale monitoring.
breadcrumbs: >-
  Docs > Datadog Security > Code Security > Static Code Analysis (SAST) > SAST
  Rules > Avoid allowing access to unintended directories or files
---

# Avoid allowing access to unintended directories or files

{% callout %}
# Important note for users on the following Datadog sites: app.ddog-gov.com

{% alert level="danger" %}
This product is not supported for your selected [Datadog site](https://docs.datadoghq.com/getting_started/site). ().
{% /alert %}

{% /callout %}

## Metadata{% #metadata %}

**ID:** `javascript-express/path-traversal`

**Language:** JavaScript

**Severity:** Warning

**Category:** Security

**CWE**: [22](https://cwe.mitre.org/data/definitions/22.html)

**Related CWEs**:

- [23](https://cwe.mitre.org/data/definitions/23.html)
- [36](https://cwe.mitre.org/data/definitions/36.html)

## Description{% #description %}

By not sanitizing user input prior to using it in path resolution methods you open your application's access to unintended directories and files.

If you're using `replace` on a user input, this rule will assume you've done so correctly and will not report a violation

#### Learn More{% #learn-more %}

- [OWASP path traversal](https://owasp.org/www-community/attacks/Path_Traversal)

## Non-Compliant Code Examples{% #non-compliant-code-examples %}

```javascript
const path = require("path");

app.get("/", (req, res) => {
  path.join("/user/", req.params.path)

  var pathname = path.join("/public/", req.body.foo)
  path.resolve(pathname)

  path.resolve(__dirname, req.body.foo)
  path.resolve(__dirname, `${req.body.foo}`)
})
```

## Compliant Code Examples{% #compliant-code-examples %}

```javascript
const path = require("path");

app.get("/", (req, res) => {
  path.join("/user/", req.params.path.replace(/^(\.\.(\/|\\|$))+/, ''))

  var pathname = path.join("/public/", req.body.foo.replace(/^(\.\.(\/|\\|$))+/, ''))
  path.resolve(pathname)

  path.resolve(__dirname, req.body.foo.replace(/^(\.\.(\/|\\|$))+/, ''))
  path.resolve(__dirname, `${req.body.foo.replace(/^(\.\.(\/|\\|$))+/, '')}`)
})
```
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