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GHSA-gx55-f84r-v3r7
No affected components available
Summary
Fission's Environment CRD exposes spec.runtime.podSpec and spec.builder.podSpec, which are merged into the Kubernetes pod specs for runtime and builder pods. The merge logic propagated hostNetwork, hostPID, hostIPC, container
privileged, and serviceAccountName from the user-supplied podspec with no filtering, and Environment.Validate performed no security-relevant checks on these fields.
Details
A namespace user with create/update on environments.fission.io could produce privileged, host-network, hostPID pods in the Fission function or builder namespace. Because the Helm chart created the fission-function and
fission-builder namespaces with no pod-security.kubernetes.io/enforce labels, Kubernetes Pod Security Admission did not catch the escape either.
From a host-network privileged pod with hostPID, the attacker could nsenter into the host, read cloud-metadata credentials, access the container-runtime socket, pivot to other namespaces, and fully compromise the node.
Impact
environments.fission.io create/update RBAC is escalated to node compromise — host filesystem and network access on the scheduling node, and from there potential cluster-wide takeover.
Fix
Fixed in #3391 and released in v1.24.0. Denylist at admission (the primary defence) plus belt-and-braces at the merge layer.
Admission denylist (pkg/apis/core/v1/podspec_safety.go::ValidatePodSpecSafety), called from Environment.Validate for both Runtime.PodSpec and Builder.PodSpec:
- pod-level:
HostNetwork,HostPID,HostIPC,ServiceAccountName/DeprecatedServiceAccountoverride, hostPath volumes; - per-container:
SecurityContext.Privileged=true,SecurityContext.AllowPrivilegeEscalation=true, dangerous capabilities (SYS_ADMIN,NET_ADMIN,SYS_PTRACE,SYS_MODULE,DAC_READ_SEARCH,DAC_OVERRIDE).
Update-bypass closed: the Environment validating-webhook marker is extended from verbs=create to verbs=create;update (chart and envtest manifests aligned).
Merge-layer belt-and-braces (pkg/executor/util/merge.go): even if admission is bypassed (failurePolicy=Ignore or stale pre-webhook objects), the denylisted pod-level fields are stripped and per-container dangerous settings are
sanitized before the merge (with SecurityContext deep-copied first so cached informer objects are not mutated). Legitimate operator hardening via the chart's pod-level securityContext (fsGroup, runAsNonRoot, runAsUser) still flows
through.
Behavioural change
Environments that explicitly set any denylisted field are now rejected at admission. There is no legitimate Fission use case — these primitives exist for cluster operators, not Environment authors.
This is the same root cause and fix as GHSA-wmgg-3p4h-48x7.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Active exploitation in the wild has been confirmed. Immediate patching or mitigation is required.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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