Beam Cloud Beta9 worker up to 0.1.755 Buildah Run Steps access control

Summaryinfo

A vulnerability was found in Beam Cloud Beta9 worker up to 0.1.755 and classified as very critical. Affected by this issue is some unknown functionality of the component Buildah Run Steps. Such manipulation leads to access control. This vulnerability is referenced as CVE-2026-120306. It is possible to launch the attack remotely. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Beam Cloud Beta9 worker up to 0.1.755. It has been rated as very critical. Affected by this issue is an unknown code of the component Buildah Run Steps. The manipulation with an unknown input leads to a access control vulnerability. Using CWE to declare the problem leads to CWE-284. The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Beta9 turns each shell command in a tenant image definition into a Dockerfile RUN line and executes it with Buildah on the build worker. The worker image sets BUILDAH_ISOLATION=chroot, and no buildah invocation passes --isolation, so the step only changes its filesystem root. It keeps the worker pod's PID, network, IPC, and user namespaces, runs as uid 0, and holds CAP_DAC_OVERRIDE. PID 1 in that procfs is the worker entrypoint, so /proc/1/root is the worker container's filesystem and is writable. That filesystem contains the runc, buildah, and runsc binaries the worker uses to start tenant containers, the worker's Kubernetes service account token, and the host directories mounted into the pod. Worker pods are privileged. Clip v2 layered builds are the default, so a tenant with a workspace token reaches this by submitting one image build. The read-only proof confirmed the shared namespaces, CAP_DAC_OVERRIDE, and that the worker's runc binary is visible at /proc/1/root. Fixed in worker 0.1.756: Buildah RUN steps, including the WORKDIR mkdir, use OCI isolation with private PID, IPC, and network namespaces, and tenant ARG values are passed only into the build container.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-120306 since 11/01/2026. The exploitation is known to be easy. The attack may be launched remotely. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 11/01/2026). This vulnerability is assigned to T1068 by the MITRE ATT&CK project.

Upgrading to version 0.1.756 eliminates this vulnerability.

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Productinfo

Type

• Cloud Software

Vendor

• Beam Cloud

Name

• Beta9 worker

Version

• 0.1.755

CPE 2.3info

• 🔒

CPE 2.2info

• 🔒

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If you want to get best quality of vulnerability data, you may have to visit VulDB.

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