A flaw was found in Helm, a tool for managing Charts, a pre-configured Kubernetes resources. Versions prior to 3.10.3 are subject to Uncontrolled Resource Consumption. Input to functions in the strvals package could cause a stack overflow that is unrecoverable by Go. Applications that use functions from the strvals package in Helm SDK may result in a denial of service.

Impact

During a security audit of Helm's code base, Helm maintainers identified a bug in which a Helm plugin can contain duplicates of the same entry, with the last one always used. If a plugin is compromised, this lowers the level of access that an attacker needs to modify a plugin's install hooks, causing a local execution attack.

To perform this attack, an attacker must have write access to the git repository or plugin archive (.tgz) while being downloaded (which can occur during a MITM attack on a non-SSL connection).

Patches

This issue has been patched in Helm 2.16.11 and Helm 3.3.2.

Workarounds

Make sure to install plugins using a secure connection protocol like SSL.

Fuzz testing, by Ada Logics and sponsored by the CNCF, identified input to functions in the strvals package that can cause an out of memory panic. Out of memory panics cannot be recovered from. Applications that use functions from the strvals package in the Helm SDK can have a Denial of Service attack when they use this package and it panics.

Impact

The strvals package contains a parser that turns strings into Go structures. For example, the Helm client has command line flags like --set, --set-string, and others that enable the user to pass in strings that are merged into the values. The strvals package converts these strings into structures Go can work with. Some string inputs can cause array data structures to be created causing an out of memory panic.

Applications that use the strvals package in the Helm SDK to parse user supplied input can suffer a Denial of Service when that input causes a panic that cannot be recovered from.

The Helm Client will panic with input to --set, --set-string, and other value setting flags that causes an out of memory panic. Helm is not a long running service so the panic will not affect future uses of the Helm client.

Patches

This issue has been resolved in 3.9.4.

Workarounds

SDK users can validate strings supplied by users won't create large arrays causing significant memory usage before passing them to the strvals functions.

For more information

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

Credits

Disclosed by Ada Logics in a fuzzing audit sponsored by CNCF.

Flux2 is a tool for keeping Kubernetes clusters in sync with sources of configuration, and Flux's helm-controller is a Kubernetes operator that allows one to declaratively manage Helm chart releases. Helm controller is tightly integrated with the Helm SDK. A vulnerability found in the Helm SDK that affects flux2 v0.0.17 until v0.32.0 and helm-controller v0.0.4 until v0.23.0 allows for specific data inputs to cause high memory consumption. In some platforms, this could cause the controller to panic and stop processing reconciliations. In a shared cluster multi-tenancy environment, a tenant could create a HelmRelease that makes the controller panic, denying all other tenants from their Helm releases being reconciled. Patches are available in flux2 v0.32.0 and helm-controller v0.23.0.

A flaw was found in Helm. Applications that use the repo package in Helm SDK to parse an index file may suffer a denial of service when that input causes a panic that cannot be recovered from. The Helm Client will panic with an index file that causes a memory violation panic.

Impact

During a security audit of Helm's code base, security researchers at Trail of Bits identified a bug in which the alias field on a Chart.yaml is not properly sanitized. This could lead to the injection of unwanted information into a chart.

Patches

This issue has been patched in Helm 3.3.2 and 2.16.11

Specific Go Packages Affected helm.sh/helm/v3/pkg/chartutil

Workarounds

Manually review the dependencies field of any untrusted chart, verifying that the alias field is either not used, or (if used) does not contain newlines or path characters.

Impact

During a security audit of Helm's code base, security researchers at Trail of Bits identified a bug in which the a Helm repository can contain duplicates of the same chart, with the last one always used. If a repository is compromised, this lowers the level of access that an attacker needs to inject a bad chart into a repository.

To perform this attack, an attacker must have write access to the index file (which can occur during a MITM attack on a non-SSL connection).

Specific Go Packages Affected helm.sh/helm/v3/pkg/repo

Patches

This issue has been patched in Helm 3.3.2 and 2.16.11

Workarounds

- do not install charts from repositories you do not trust - fetch charts using a secure channel of communication (such as TLS) - use helm pull to fetch the chart, then review the chart’s content (either manually, or with helm verify if it has been signed) to ensure it has not been tampered with - manually review the index file in the Helm repository cache before installing software.

Impact

Security researchers at Trail of Bits discovered that plugin names are not sanitized properly. As a result, a malicious plugin author could use characters in a plugin name that would result in unexpected behavior, such as duplicating the name of another plugin or spoofing the output to helm --help.

Specific Go Packages Affected helm.sh/helm/v3/pkg/plugin

Patches

This issue has been patched in Helm 3.3.2.

Workarounds

Do not install untrusted Helm plugins. Examine the name field in the plugin.yaml file for a plugin, looking for characters outside of the [a-zA-Z0-9.-] range.

In Helm greater than or equal to 3.0.0 and less than 3.2.4, a path traversal attack is possible 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. This has been fixed in 3.2.4.

Helm could allow a local authenticated attacker to bypass security restrictions, caused by the failure to sanitized multiple fields in various .yaml files. By sending a specially-crafted request, an attacker could exploit this vulnerability to send deceptive, obscure or alter information to a terminal screen.