CVE-2026-120307
CriticalCVSS 9.9Summary
The Beta9 worker serves the sandbox file API from outside the container. getHostPathFromContainerPath turns the tenant's container path into a worker path; if the unresolved path starts with a mount destination (including the default /tmp/.beta9), the remainder is joined onto that mount's source with filepath.Join, which cleans parent-directory segments after the prefix check. A long enough run of such segments names any absolute path on the worker, and a path matching no mount is opened in the worker's filesystem, following absolute symbolic links. A tenant with a workspace token and a running sandbox can read, write, list, and delete files on the worker as root, including other tenants' files.
Risk Assessment
A tenant can gain full access to the worker's filesystem as root, including the Kubernetes service account token, which in shipped manifests is bound to cluster-admin, potentially leading to cluster takeover. Affects Beta9 workers before 0.1.756.
Recommendation
Update the Beta9 worker to version 0.1.756 or later, which uses os.OpenRoot for sandbox file operations and workspace sync, keeping paths inside the container root or mount source.
Other vulnerabilities in Beta9
See all- CVE-2026-120308Critical
In Beta9, a tenant can attach a volume when deploying a function, endpoint, or task queue. The gateway builds the host path by joining the shared volumes root, the workspace name, and the volume identifier from the stub configuration, without checking that the identifier names a volume owned by that workspace. Parent-directory segments in the identifier collapse the joined path to the worker's filesystem root, which is bind-mounted read-write into the sandbox, allowing read and write access to the worker's files, including other tenants' volumes.
- CVE-2026-120306Critical
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, keeping the worker pod's PID, network, IPC, and user namespaces, running as uid 0 with 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, containing the runc, buildah, and runsc binaries, the worker's Kubernetes service account token, and host directories mounted into the pod. Worker pods are privileged, and Clip v2 layered builds are the default, so a tenant with a workspace token reaches this by submitting one image build.
Original NVD description (English source)
The Beta9 worker serves the sandbox file API from outside the container. getHostPathFromContainerPath turns the tenant's container path into a worker path. If the unresolved path starts with a mount destination, including the default upload mount at /tmp/.beta9, the remainder is joined onto that mount's source with filepath.Join, which cleans parent-directory segments after the prefix check. A long enough run of those segments names any absolute path on the worker. A path that matches no mount is joined onto the container root and opened in the worker's own filesystem, so an absolute symbolic link such as /var/run pointing at /run is followed against the worker root. Upload, download, stat, list, find-in-files, replace-in-files, and delete-file all call this helper. A tenant with a workspace token and one running sandbox can read, write, list, and delete files on the hosting worker as root, including files of other tenants on that machine. A read-only proof downloaded the worker pod's Kubernetes service account token through the file API for a path that did not exist inside the sandbox. In the shipped remote-node manifests that service account is bound to cluster-admin. Fixed in worker 0.1.756: sandbox file operations and workspace sync open paths with os.OpenRoot, so parent-directory and symlink lookups stay inside the container root or the mount source.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS