Arbitrary File Write via Archive Extraction (Zip Slip) Affecting sharpziplib package, versions [,1.0.0)


0.0
medium
  • Attack Complexity

    Low

  • User Interaction

    Required

  • Integrity

    High

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  • snyk-id

    SNYK-DOTNET-SHARPZIPLIB-60247

  • published

    11 Jun 2018

  • disclosed

    10 Jun 2018

  • credit

    Snyk Security research Team

How to fix?

Upgrade sharpziplib to version 1.0.0 or higher.

Overview

sharpziplib is a Zip, GZip, Tar and BZip2 library written entirely in C# for the .NET platform.

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