Helm Chart extraction output directory collapse via `Chart.yaml` name dot-segment

Helm is a package manager for Charts for Kubernetes. In Helm versions <=3.20.1 and <=4.1.3, a specially crafted Chart will cause helm pull --untar [chart URL | repo/chartname] to write the Chart's contents to the immediate output directory (as defaulted to the current working directory; or as given by the --destination and --untardir flags), rather than the expected output directory suffixed by the chart's name.

Impact

The bug enables writing the Chart's contents (unpackaged/untar'ed) to the output directory <output dir>/, instead of the expected <output dir>/<chart name>/, potentially overwriting the contents of the targeted directory.

Note: a chart name containing POSIX dot-dot, or dot-dot and slashes (as if to refer to parent directories) do not resolve beyond the output directory as designed.

Patches

This issue has been resolved in Helm v3.20.2 and v4.1.3

A Chart with an unexpected name (those specified to be "." or ".."), or a Chart name which results in a non-unique directory will be rejected.

Workarounds

Ensure the the name of the Chart does not comprise/contain POSIX pathname special directory references ie. dot-dot ("..") or dot ("."). In addition, ensuring that the pull --untar flag (or equivalent SDK option) refers to a unique/empty output directory prevents chart extraction from inadvertently overwriting existing files within the specified directory.

Credits

Oleh Konko
@1seal