Arbitrary File Write via Archive Extraction (Zip Slip) Affecting net.lingala.zip4j:zip4j package, versions [0,1.3.3)



    Attack Complexity Low
    User Interaction Required
    Integrity High
Expand this section
6.5 medium

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • published 31 May 2018
  • disclosed 17 Apr 2018
  • credit Snyk Security research Team

How to fix?

Upgrade net.lingala.zip4j:zip4j to version 1.3.3 or higher.


net.lingala.zip4j:zip4j is a open source java library to handle zip files.

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip). Successful exploitation of this vulnerability can result in remote command execution.


It is exploited using a specially crafted zip archive, that holds path traversal filenames. When exploited, a filename in a malicious archive is concatenated to the target extraction directory, which results in the final path ending up outside of the target folder. For instance, a zip may hold a file with a "../../file.exe" location and thus break out 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 malicous 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