Beta9 build sandbox escape via chroot-only isolation
Summary
| CVE | CVE-2026-120306 |
|---|---|
| State | PUBLISHED |
| Assigner | JFROG |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-11-01 13:18:01 UTC |
| Updated | 2026-11-02 20:17:40 UTC |
| Description | 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. |
Risk And Classification
Primary CVSS: v3.1 9.9 CRITICAL from [email protected]
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Problem Types: CWE-269 | CWE-653 | CWE-653 CWE-653: Improper Isolation or Compartmentalization | CWE-269 CWE-269: Improper Privilege Management
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 9.9 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H |
| 3.1 | CNA | CVSS | 9.9 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H |
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Beam-cloud | Beta9 Worker | affected 0.1.756 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/beam-cloud/beta9 | [email protected] | github.com | |
| github.com/beam-cloud/beta9/pull/1897 | [email protected] | github.com | |
| github.com/beam-cloud/beta9/releases/tag/worker-0.1.756 | [email protected] | github.com | |
| github.com/beam-cloud/beta9/commit/a28bf12cf0007c792a25d8ed282b4e8bf6f30393 | [email protected] | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Natan Nehorai (en)
CNA: JFrog Security Research (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-09-15T04:03:00.000Z | Fix merged in pull request 1897 (commit a28bf12) |
| CNA | 2026-09-15T04:03:00.000Z | Fixed release worker-0.1.756 published. No vendor security advisory was filed with the pull request. |
Solutions
CNA: Upgrade the Beta9 worker to 0.1.756 or later. That release drops chroot isolation: Buildah RUN steps use OCI isolation with private PID, IPC, and network namespaces, and tenant build arguments are applied inside the build container rather than in the Buildah process environment. The fix is commit a28bf12 (pull request 1897), released as worker-0.1.756 on 2026-09-15. Gateway 0.1.776 is the gateway tag cut from the same commit; the isolation change itself is in the worker image.