HCSEC-2026-21 - Nomad vulnerable to sandbox escape in Docker task driver #28177

Bulletin ID: HCSEC-2026-21

Affected Products / Versions: Nomad and Nomad Enterprise up to 2.0.3; fixed in Nomad 2.0.4 and Nomad Enterprise 2.0.4, 1.11.8, and 1.10.14.

Publication Date: July 8, 2026

Summary

HashiCorp Nomad and Nomad Enterprise are vulnerable to a sandbox escape in the Docker task driver that may allow a job submitter to bind-mount a host path into a container even when volume bind mounts are disabled, potentially leading to reading and writing files on the host. This vulnerability, CVE-2026-14891, is fixed in Nomad Community Edition 2.0.4 and Nomad Enterprise 2.0.4, 1.11.8, and 1.10.14.

Background

Nomad’s Docker task driver lets a task bind-mount paths into its container. When volume bind mounts are disabled (the default), the driver restricts these bind mounts so that a task may only mount paths contained within its own allocation directory and may not mount arbitrary host paths.

Details

The driver’s containment check did not fully account for symbolic links when validating a bind mount, so a mount that resolved to a location outside the allocation directory could be permitted. This may allow a job to bind-mount a host path into its container and read or write files on the host filesystem, escaping the allocation sandbox, even when volume bind mounts are disabled. Exploitation requires the ability to submit a Docker-driver job, which is an authenticated job submitter when ACLs are enabled or any API client when ACLs are disabled.

Remediation

Customers should evaluate the risk associated with this issue and consider upgrading to Nomad Community Edition 2.0.4 or Nomad Enterprise 2.0.4, 1.11.8, or 1.10.14.

Acknowledgement

This issue was reported to HashiCorp by Volkan Kutal, GitHub handle @KutalVolkan.

We deeply appreciate any effort to coordinate disclosure of security vulnerabilities. For information about security at HashiCorp and the reporting of security vulnerabilities, please see https://hashicorp.com/security.