Arbitrary File Write via Archive Extraction (Zip Slip) Affecting rubyzip package, versions <1.2.1
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Test your applications- Snyk ID SNYK-RUBY-RUBYZIP-20336
- published 6 Mar 2017
- disclosed 3 Feb 2017
- credit ecneladis
How to fix?
Upgrade rubyzip to version 1.2.1 or higher.
Overview
rubyzip is rubyzip is a ruby module for reading and writing zip files.
Affected versions of the package are vulnerable to Arbitrary File Write via Archive Extraction (AKA "Zip Slip").
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