CVE-2026-120306

What it is

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.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of data exposure, data tampering, service disruption.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-11-01 12:32 UTC ReservedThe CVE id was reserved by its CNA
2. 2026-11-01 13:18 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-11-02 20:17 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.4% in the next 30 days (EPSS).
• Severity: 9.9 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-11-01 13:18 UTC

Last modified

2026-11-02 20:17 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-269 · Improper privilege management

Record status

Deferred

Attack profile CVSS 3.1 · 9.9

Attack vector

Network

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-120306.md and follow it. Check whether this project is affected by CVE-2026-120306. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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