Helm vulnerable to information disclosure via getHostByName Function

A Helm contributor discovered an information disclosure vulnerability using the getHostByName template function.

Impact

getHostByName is a Helm template function introduced in Helm v3. The function is able to accept a hostname and return an IP address for that hostname. To get the IP address the function performs a DNS lookup. The DNS lookup happens when used with helm install|upgrade|template or when the Helm SDK is used to render a chart.

Information passed into the chart can be disclosed to the DNS servers used to lookup the IP address. For example, a malicious chart could inject getHostByName into a chart in order to disclose values to a malicious DNS server.

Patches

The issue has been fixed in Helm 3.11.1.

Workarounds

Prior to using a chart with Helm verify the getHostByName function is not being used in a template to disclose any information you do not want passed to DNS servers.

For more information

Helm's security policy is spelled out in detail in our SECURITY document.

Credits

Disclosed by Philipp Stehle at SAP.