{"id":"CVE-2026-50566","aliases":["GHSA-m63v-2g9w-2w6v","GO-2026-5857"],"url":"https://o3.security/vulnerability/CVE-2026-50566","summary":"Fission: Environment Runtime.Container and Builder.Container SecurityContext bypass allows privileged pod creation","details":"### Summary\n\nA follow-up bypass of the round-4 PodSpec hardening (GHSA-gx55-f84r-v3r7, GHSA-wmgg-3p4h-48x7, GHSA-v455-mv2v-5g92). Those advisories validate and sanitize the `PodSpec` (`spec.runtime.podSpec` / `spec.builder.podSpec` /\n`function.spec.podSpec`), but the Environment CRD also exposes `spec.runtime.container` and `spec.builder.container` — a standalone `Container` merged into the runtime/builder pod whose `SecurityContext` bypassed both layers.\n\n### Details\n\n**Admission-layer gap.** `Environment.Validate()` calls `ValidatePodSpecSafety()` on `Runtime.PodSpec` and `Builder.PodSpec` only. That function takes a `*PodSpec`, so it never inspects the standalone `Runtime.Container.SecurityContext`\nor `Builder.Container.SecurityContext`.\n\n**Merge-layer gap.** `sanitizeContainerSecurityContext()` ran only inside `MergePodSpec()`. The container field is merged via `MergeContainer()`, which did not sanitize. With only `Runtime.Container` set and `Runtime.PodSpec` nil,\n`MergePodSpec` is never invoked, so the sanitizer never ran.\n\nAffected merge sites: poolmgr (`gp_deployment.go`), newdeploy (`newdeploy.go`), and buildermgr (`envwatcher.go`).\n\n#### Proof of concept\n\n```yaml\napiVersion: fission.io/v1\nkind: Environment\nmetadata:\n  name: priv-escape-test\n  namespace: default\nspec:\n  version: 3\n  runtime:\n    image: \"ghcr.io/fission/python-env:latest\"\n    container:\n      name: priv-escape-test\n      securityContext:\n        privileged: true\n  poolsize: 1\n```\n\nThe admission webhook accepts this Environment and the resulting pool pod runs with `privileged: true`. Equivalent bypasses: `allowPrivilegeEscalation: true`, `capabilities.add: [\"SYS_ADMIN\"]`, `capabilities.add:\n[\"NET_ADMIN\",\"SYS_PTRACE\"]`. The same attack applies to `Builder.Container`.\n\n### Impact\n\nA tenant with `environments.fission.io` create/update RBAC can run `privileged` / `allowPrivilegeEscalation` / dangerous-capability containers in the Fission function or builder namespace, scheduled under the executor's high-privilege\nservice account — enabling container-sandbox escape, host filesystem and network access, and potential node- and cluster-level compromise. Identical blast radius to GHSA-gx55-f84r-v3r7.\n\n### Fix\n\nFixed in [#3406](https://github.com/fission/fission/pull/3406) and released in [v1.24.0](https://github.com/fission/fission/releases/tag/v1.24.0).\n\n- **Admission layer (primary defence):** a new `ValidateContainerSafety` in `pkg/apis/core/v1/podspec_safety.go` applies the per-container SecurityContext denylist (`privileged`, `allowPrivilegeEscalation`, dangerous capabilities) to a\nstandalone container, and is called from `Environment.Validate()` for `Runtime.Container` and `Builder.Container`.\n- **Merge layer (defence in depth):** `sanitizeContainerSecurityContext()` is now invoked inside `MergeContainer()` itself, covering all three executor/builder call sites.\n\n### Workarounds\n\n- Restrict Environment create/update RBAC to trusted administrators.\n- Deploy a Kyverno / OPA Gatekeeper policy rejecting dangerous Container SecurityContext on Environment CRDs.\n- Label the function/builder namespaces with `pod-security.kubernetes.io/enforce: restricted`.\n\n### References\n\n- GHSA-gx55-f84r-v3r7, GHSA-wmgg-3p4h-48x7, GHSA-v455-mv2v-5g92 — the round-4 PodSpec fixes this advisory bypasses ([#3391](https://github.com/fission/fission/pull/3391), `e484df84`).","published":"2026-06-10T17:29:35.349Z","modified":"2026-08-12T03:51:38.983811894Z","cvss":{"score":9.9,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"},"epss":{"score":0.0029,"percentile":0.21631,"asOf":"2026-09-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/fission/fission","fixedVersion":"1.24.0"}],"fix":{"url":"https://github.com/fission/fission/pull/3406","label":"fission/fission#3406"},"references":[{"type":"WEB","url":"https://github.com/fission/fission/releases/tag/v1.24.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/50xxx/CVE-2026-50566.json"},{"type":"ADVISORY","url":"https://github.com/fission/fission/security/advisories/GHSA-m63v-2g9w-2w6v"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-50566"},{"type":"FIX","url":"https://github.com/fission/fission/pull/3406"},{"type":"WEB","url":"https://github.com/fission/fission/commit/695d3e97e3a20463ab7c8c081843e69e65e952e5"},{"type":"PACKAGE","url":"https://github.com/fission/fission"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:38.983811894Z"}}