CVE-2019-18658

The vulnerability resides in the Helm 2.x client versions prior to 2.15.2. When processing chart directories or packaging charts, the client follows symbolic links (symlinks) present in the chart. An attacker can craft a chart that includes symlinks pointing to sensitive local files such as /etc/passwd or to special files like /dev/urandom. This allows the client to inadvertently read and include the contents of those files [1].

Exploitation requires no authentication; an attacker simply supplies a malicious chart to a victim. If the victim runs commands such as helm package, helm lint, or any operation that loads a chart from a directory, the client will follow the symlinks. The victim's machine processes the chart, potentially exposing sensitive data or hanging indefinitely due to blocking reads from /dev/urandom [1].

The impact is twofold: information disclosure of sensitive system files and denial of service. This vulnerability does not affect the Tiller server component; it is purely client-side. Any user who processes untrusted charts is at risk [1].

Mitigation is straightforward: upgrade to Helm version 2.15.2 or later. There is no known workaround other than avoiding untrusted charts. The issue is fixed in the referenced release [1].