Arbitrary File Read Affecting sulu/sulu package, versions >=0.0.0, <1.6.44>=2.0.0, <2.2.18>=2.3.0, <2.3.8


Severity

Recommended
0.0
high
0
10

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

Threat Intelligence

EPSS
0.3% (71st percentile)

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  • Snyk IDSNYK-PHP-SULUSULU-2320795
  • published16 Dec 2021
  • disclosed16 Dec 2021
  • creditUnknown

Introduced: 16 Dec 2021

CVE-2021-43836  (opens in a new tab)
CWE-22  (opens in a new tab)

How to fix?

Upgrade sulu/sulu to version 1.6.44, 2.2.18, 2.3.8 or higher.

Overview

sulu/sulu is a highly extensible open-source PHP content management system based on the Symfony framework.

Affected versions of this package are vulnerable to Arbitrary File Read via a PHP file include. In a default configuration, this also leads to remote code execution.

###Workaround Overwrite the service sulu_route.generator.expression_token_provider and wrap the translator before passing it to the expression language.

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

References

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