Directory Traversal Affecting marked-tree package, versions *


Severity

Recommended
0.0
high
0
10

CVSS assessment made by Snyk's Security Team. Learn more

Threat Intelligence

Exploit Maturity
Proof of concept
EPSS
0.64% (80th percentile)

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  • Snyk IDSNYK-JS-MARKEDTREE-590121
  • published20 Jun 2020
  • disclosed20 Jun 2020
  • creditJHU System Security Lab

Introduced: 20 Jun 2020

CVE-2020-7682  (opens in a new tab)
CWE-22  (opens in a new tab)

How to fix?

There is no fixed version for marked-tree.

Overview

marked-tree is a markdown viewer for viewing markdown within a development environment.

Affected versions of this package are vulnerable to Directory Traversal. There is no path sanitization in the path provided at fs.readFile in index.js.

PoC by JHU System Security Lab

  1. Start the server node index.js
  2. Create a file sensitive-file in the server's parent directory
  3. curl -s --path-as-is http://127.0.0.1:3500/../sensitive-file

Details

A Directory Traversal attack (also known as path traversal) aims to access files and directories that are stored outside the intended folder. By manipulating files with "dot-dot-slash (../)" sequences and its variations, or by using absolute file paths, it may be possible to access arbitrary files and directories stored on file system, including application source code, configuration, and other critical system files.

Directory Traversal vulnerabilities can be generally divided into two types:

  • Information Disclosure: Allows the attacker to gain information about the folder structure or read the contents of sensitive files on the system.

st is a module for serving static files on web pages, and contains a vulnerability of this type. In our example, we will serve files from the public route.

If an attacker requests the following URL from our server, it will in turn leak the sensitive private key of the root user.

curl http://localhost:8080/public/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/root/.ssh/id_rsa

Note %2e is the URL encoded version of . (dot).

  • Writing arbitrary files: Allows the attacker to create or replace existing files. This type of vulnerability is also known as Zip-Slip.

One way to achieve this is by using a malicious zip archive that holds path traversal filenames. When each filename in the zip archive gets concatenated to the target extraction folder, without validation, the final path ends up outside of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicious file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:

2018-04-15 22:04:29 .....           19           19  good.txt
2018-04-15 22:04:42 .....           20           20  ../../../../../../root/.ssh/authorized_keys

CVSS Scores

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