CVE-2026-50566

### Summary A 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` / `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. ### Details **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` or `Builder.Container.SecurityContext`. **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, `MergePodSpec` is never invoked, so the sanitizer never ran. Affected merge sites: poolmgr (`gp_deployment.go`), newdeploy (`newdeploy.go`), and buildermgr (`envwatcher.go`). #### Proof of concept ```yaml apiVersion: fission.io/v1 kind: Environment metadata: name: priv-escape-test namespace: default spec: version: 3 runtime: image: "ghcr.io/fission/python-env:latest" container: name: priv-escape-test securityContext: privileged: true poolsize: 1 ``` The admission webhook accepts this Environment and the resulting pool pod runs with `privileged: true`. Equivalent bypasses: `allowPrivilegeEscalation: true`, `capabilities.add: ["SYS_ADMIN"]`, `capabilities.add: ["NET_ADMIN","SYS_PTRACE"]`. The same attack applies to `Builder.Container`. ### Impact A 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'