Arbitrary File Write via Archive Extraction (Zip Slip) Affecting package, versions <1.49.4

  • Attack Complexity


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  • snyk-id


  • published

    11 Oct 2019

  • disclosed

    11 Sep 2019

  • credit

    Semmle Security Research

How to fix?

Upgrade to version 1.49.4 or higher.

Overview is a package part of rclone - "rsync for cloud storage".

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip). Files within a zip file can break out of the target directory when being extracted.


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