The Helm core maintainers have identified an information disclosure vulnerability in Helm 3.0.0-3.1.2.
lookup
is a Helm template function introduced in Helm v3. It is able to lookup resources in the cluster to check for the existence of specific resources and get details about them. This can be used as part of the process to render templates.
The documented behavior of helm template
states that it does not attach to a remote cluster. However, as the recently added lookup
template function circumvents this restriction and connects to the cluster even during helm template
and helm install|update|delete|rollback --dry-run
. The user is not notified of this behavior.
Running helm template
should not make calls to a cluster. This is different from install
, which is presumed to have access to a cluster in order to load resources into Kubernetes. Helm 2 is unaffected by this vulnerability.
A malicious chart author could inject a lookup
into a chart that, when rendered through helm template
, performs unannounced lookups against the cluster a user's KUBECONFIG
file points to. This information can then be disclosed via the output of helm template
.
This issue has been fixed in Helm 3.2.0
Due to another bug (also fixed in Helm 3.2.0), the command helm lint
will fail with an error if the lookup
function is used in a chart. Therefore, run helm lint
on an untrusted chart before running helm template
.
Alternately, setting the KUBECONFIG
environment variable to point to an empty Kubernetes configuration file will prevent unintended network connections.
Finally, a chart may be manually analyzed for the presence of a lookup
function in any file in the templates/
directory.
If you have any questions or comments about this advisory: * Open an issue in the Helm repository * For security-specific issues, email us at cncf-helm-security@lists.cncf.io
{ "nvd_published_at": null, "github_reviewed_at": "2021-05-24T21:15:16Z", "severity": "HIGH", "github_reviewed": true, "cwe_ids": [ "CWE-200" ] }