GMS-2021-89: chroot isolation: environment value leakage to intermediate processes

Impact

When running processes using “chroot” isolation, the process being run can examine the environment variables of its immediate parent and grandparent processes (CVE-2021-3602). This isolation type is often used when running buildah in unprivileged containers, and it is often used to do so in CI/CD environments. If sensitive information is exposed to the original buildah process through its environment, that information will unintentionally be shared with child processes which it starts as part of handling RUN instructions or during buildah run. The commands that buildah is instructed to run can read that information if they choose to.

Patches

Users should upgrade packages, or images which contain packages, to include version 1.21.3 or later.

Workarounds

As a workaround, invoking buildah in a container under env -i to have it started with a reinitialized environment should prevent the leakage.

For more information

If you have any questions or comments about this advisory:

• Open an issue in buildah
• Email us at the buildah general mailing list, or the podman security mailing list if it’s sensitive.