CVE-2026-14891: HashiCorp Nomad Docker Driver Sandbox Escape

Technical summary

The vulnerability exists in Nomad's Docker task driver implementation, where insufficient validation of mount parameters allows privileged users to perform a sandbox escape. Specifically, the flaw enables binding host paths into container filesystems regardless of the bind-mount configuration setting that administrators use to restrict this capability. This represents a security model bypass rather than a simple misconfiguration issue. The root cause involves inadequate separation between allowed and disallowed mount operations, permitting job submitters to circumvent intended access controls. The CVSS 3.1 score of 8.7 reflects high confidentiality and integrity impact with network-adjacent attack surface, though exploitation requires elevated privileges (job submission rights).

Business impact

Organizations running Nomad face direct exposure of host filesystem data and potential integrity compromise. In multi-tenant or shared infrastructure scenarios, a job submitter—who may have limited intended permissions—can read private keys, configuration files, application secrets, and other sensitive data stored on the host. This undermines the security isolation model that containerization and orchestration platforms are designed to provide. The ability to write files could enable persistence mechanisms, privilege escalation, or lateral movement. Particularly in regulated industries (finance, healthcare, government), this could trigger compliance violations and incident response obligations.

Affected systems

Nomad Community Edition versions prior to 2.0.4 are vulnerable, as are Nomad Enterprise versions prior to 2.0.4, 1.11.8, and 1.10.14. Organizations running any version at or above these patched releases are protected. The scope of impact depends on deployment architecture: environments where external or untrusted users can submit jobs face higher risk than those with strictly controlled submission access.

Exploitability

Exploitation requires valid job submission credentials—the attacker must be able to author and submit jobs to the Nomad cluster. This eliminates opportunistic remote exploitation from the internet, but in environments where job submission is delegated to developers, CI/CD systems, or third-party services, the barrier is considerably lower. Once a job is submitted with a crafted task driver configuration exploiting this flaw, the escape executes automatically when the container starts. No user interaction or additional exploitation steps are needed. The attack is deterministic and reliable.

Remediation

Upgrade Nomad Community Edition to 2.0.4 or later, or upgrade Enterprise Edition to 2.0.4, 1.11.8, or 1.10.14 depending on your current version track. HashiCorp has released patched versions across multiple release branches to accommodate different organizational upgrade cadences. After patching, verify that the Docker task driver no longer permits unauthorized bind mounts by reviewing task job definitions and testing with sample configurations that attempt to mount host paths. Additionally, audit existing jobs for suspicious mount configurations that may have been deployed before the patch.

Patch guidance

Apply the relevant patched version matching your current Nomad edition and release line. Community Edition users should upgrade to 2.0.4. Enterprise Edition users on the 2.0.x line should upgrade to 2.0.4, those on 1.11.x to 1.11.8, and those on 1.10.x to 1.10.14. Schedule patching during a maintenance window, as it requires Nomad cluster restart or rolling upgrade depending on your architecture. Test the upgrade in a non-production environment first to validate compatibility with your job configurations and any custom task driver plugins. Review HashiCorp's official upgrade documentation for any breaking changes or additional steps specific to your version path.

Detection guidance

Search your Nomad job definitions and running containers for mount directives that reference host paths, particularly those in the docker task driver configuration. Look for volume and mount blocks that specify host_path or similar parameters. Since administrators typically disable bind mounts via policy, any legitimate mounts should be well-documented. Check Nomad audit logs for job submissions containing suspicious Docker driver configurations. Monitor running containers for unexpected volume mounts using docker inspect or container runtime introspection tools. If you discover unintended mounts, immediately stop affected jobs and investigate for data exfiltration or host compromise.

Why prioritize this

This vulnerability combines high impact (full read/write access to host filesystem) with moderate exploitability (requires job submission rights). In environments with permissive job submission policies or where external systems submit jobs, the risk is acute. The sandbox escape nature of the flaw—enabling circumvention of explicitly-set security policies—makes it a priority fix regardless of deployment model. The availability of patches across multiple version lines reduces disruption to patching schedules.

Risk score, explained

The CVSS 3.1 score of 8.7 (HIGH) reflects significant confidentiality and integrity impact to the host system, combined with network-adjacent attack surface and the requirement for high privileges (job submitter role). The score appropriately captures the severity of sandbox escape vulnerabilities, which undermine the core security model of containerized systems. Organizations should treat this as urgent but not immediately critical in the absence of external exploit demonstrations or active threat activity.

Frequently asked questions