A recently identified vulnerability tracked under the Common Vulnerabilities and Exposures (CVE) identifier CVE-2024-36137 has been discovered in Node.js. The vulnerability affects the experimental permission model used in certain Node.js applications, and it specifically impacts those that use the --allow-fs-write flag during their operations. This potentially allows an attacker to bypass file permission restrictions by employing specific file system operations like fs.fchown or fs.fchmod.

Exploit Details

Being Node.js an open-source platform, it enables developers to build network and server-side applications using JavaScript. The experimental permission model in Node.js is an access control mechanism that provides security configurations for file operations, thus preventing unauthorized actions. A key point to highlight is that this model doesn't work directly on file descriptors.

During normal execution, a file descriptor is a unique identifier (a non-negative integer) that refers to an open file within a process. A vulnerability exists when users have enabled the experimental permission model in their Node.js applications and are using the --allow-fs-write flag. This flag permits file system write operations that would otherwise be restricted.

The issue arises when operations such as fs.fchown or fs.fchmod are employed. These operations can utilize a "read-only" file descriptor to modify file ownership and permissions. Consequently, an attacker could potentially exploit this flaw to bypass the read-only restriction and alter sensitive data or system files.

Affected Versions

Node.js applications employing the experimental permission model and relying on the --allow-fs-write flag are susceptible to the vulnerability. As of the time of writing this post, the affected versions have not been explicitly stated. As more information emerges, users should check Node.js official channels for updates on affected versions and any subsequent patches released.

Mitigating the Vulnerability

Till now, there has been no official fix released to address the CVE-2024-36137 vulnerability. However, users must be cautious when employing the experimental permission model and using the --allow-fs-write flag in their applications. If possible, avoid using these features until a security patch is issued by the Node.js development team.

Additionally, users should adopt secure coding practices when working with file operations. For example, avoiding the use of functions such as fs.fchown or fs.fchmod when you don't need their specific functionality. Use other file permission-related functions that don't suffer from this vulnerability.

Here is an example of the problematic code

// Example of vulnerable usage of fs.fchown
// Where the fd might be a "read-only" file descriptor

const fs = require('fs');
const fd = fs.openSync('myfile.txt', 'r');

fs.fchown(fd, uid, gid, (err) => {
  if (err) console.log(Error: ${err});
  else console.log('Ownership changed successfully');
});

// Example of vulnerable usage of fs.fchmod
// Where the fd might be a "read-only" file descriptor

const fs = require('fs');
const fd = fs.openSync('myfile.txt', 'r');

fs.fchmod(fd, '600', (err) => {
  if (err) console.log(Error: ${err});
  else console.log('Permissions changed successfully');
});

Original References

For original references, users can consult the Node.js project homepage, the project's GitHub repository, and the Node.js blog. More information about this particular vulnerability will be available from these sources as it becomes available. Here are some helpful links:

- Node.js Homepage: https://nodejs.org
- Node.js GitHub Repository: https://github.com/nodejs/node
- Node.js Blog: https://nodejs.org/en/blog

TL;DR Summary

CVE-2024-36137 is a vulnerability in Node.js experimental permission model that affects applications using the --allow-fs-write flag. The flaw allows an attacker to exploit specific file system operations such as fs.fchown or fs.fchmod, which can use a "read-only" file descriptor to alter a file's permissions and ownership. Users must be cautious when using the experimental permission model and the --allow-fs-write flag until an official patch is available.

Timeline

Published on: 09/07/2024 16:15:02 UTC
Last modified on: 11/22/2024 12:15:18 UTC