CVE-2026-120306 (GCVE-0-2026-120306)

Vulnerability from cvelistv5 – Published: 2026-11-01 12:49 – Updated: 2026-11-01 12:49
VLAI
Title
Beta9 build sandbox escape via chroot-only isolation
Summary
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.
Severity
9.9 (Critical)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
CWE
  • CWE-653 - Improper Isolation or Compartmentalization
  • CWE-269 - Improper Privilege Management
Assigner
JFROG CNA under the mitre root
CNA scorecard B 76/100 over 66 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
beam-cloud Beta9 worker Affected: 0 , < 0.1.756 (semver)
guessed Create a notification for this product.
Credits
Natan Nehorai JFrog Security Research
Show details on NVD website
To clipboard 

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          "defaultStatus": "unaffected",
          "packageName": "github.com/beam-cloud/beta9",
          "product": "Beta9 worker",
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            "pkg/worker/image.go",
            "pkg/worker/image_build_layered.go",
            "pkg/abstractions/image/builder.go",
            "pkg/scheduler/pool_local.go"
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          "repo": "git://github.com/beam-cloud/beta9",
          "vendor": "beam-cloud",
          "versions": [
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              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
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      "credits": [
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          "type": "finder",
          "value": "Natan Nehorai"
        },
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          "type": "coordinator",
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              "value": "\u003cp\u003eBeta9 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\u0027s 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\u0027s filesystem and is writable. That filesystem contains the runc, buildah, and runsc binaries the worker uses to start tenant containers, the worker\u0027s 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\u0027s 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.\u003c/p\u003e"
            }
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            "baseScore": 9.9,
            "baseSeverity": "CRITICAL",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "scope": "CHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
            "version": "3.1"
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              "value": "Default clip v2 layered image build on a privileged build-pool worker"
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              "description": "CWE-269: Improper Privilege Management",
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      "providerMetadata": {
        "dateUpdated": "2026-11-01T12:49:05.857Z",
        "orgId": "48a46f29-ae42-4e1d-90dd-c1676c1e5e6d",
        "shortName": "JFROG"
      },
      "references": [
        {
          "name": "Beta9 repository",
          "tags": [
            "product"
          ],
          "url": "https://github.com/beam-cloud/beta9"
        },
        {
          "name": "Handle sandbox edge cases (fix pull request)",
          "tags": [
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          "url": "https://github.com/beam-cloud/beta9/pull/1897"
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          "tags": [
            "release-notes"
          ],
          "url": "https://github.com/beam-cloud/beta9/releases/tag/worker-0.1.756"
        }
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            }
          ],
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      "source": {
        "discovery": "EXTERNAL"
      },
      "timeline": [
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          "lang": "en",
          "time": "2026-09-15T04:03:00.000Z",
          "value": "Fix merged in pull request 1897 (commit a28bf12)"
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        {
          "lang": "en",
          "time": "2026-09-15T04:03:00.000Z",
          "value": "Fixed release worker-0.1.756 published. No vendor security advisory was filed with the pull request."
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    "cveId": "CVE-2026-120306",
    "datePublished": "2026-11-01T12:49:05.857Z",
    "dateReserved": "2026-11-01T12:32:40.057Z",
    "dateUpdated": "2026-11-01T12:49:05.857Z",
    "state": "PUBLISHED"
  },
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                  "pkg/worker/image_build_layered.go",
                  "pkg/abstractions/image/builder.go",
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        "descriptions": [
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            "value": "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\u0027s 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\u0027s filesystem and is writable. That filesystem contains the runc, buildah, and runsc binaries the worker uses to start tenant containers, the worker\u0027s 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\u0027s 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."
          }
        ],
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        "lastModified": "2026-11-01T13:18:01.300",
        "metrics": {
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                "attackVector": "NETWORK",
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                "baseSeverity": "CRITICAL",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "CHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
                "version": "3.1"
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              "exploitabilityScore": 3.1,
              "impactScore": 6.0,
              "source": "reefs@jfrog.com",
              "type": "Secondary"
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        "published": "2026-11-01T13:18:01.300",
        "references": [
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            "source": "reefs@jfrog.com",
            "url": "https://github.com/beam-cloud/beta9"
          },
          {
            "source": "reefs@jfrog.com",
            "url": "https://github.com/beam-cloud/beta9/commit/a28bf12cf0007c792a25d8ed282b4e8bf6f30393"
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            "source": "reefs@jfrog.com",
            "url": "https://github.com/beam-cloud/beta9/pull/1897"
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            "url": "https://github.com/beam-cloud/beta9/releases/tag/worker-0.1.756"
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        "vulnStatus": "Received",
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            "source": "reefs@jfrog.com",
            "type": "Primary"
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}



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