Summary
Fission Environment CRD podspec passthrough enables hostPID/hostNetwork/privileged pods, node escape
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 andfission-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.
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.
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.
The application assigns, modifies, tracks, or checks privileges incorrectly, allowing a user to gain elevated access. Typical impact: privilege escalation beyond the intended level.
CVE-2026-50564 has a CVSS score of 9.9 (Critical). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.24.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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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.
Frequently Asked Questions
- What is CVE-2026-50564? CVE-2026-50564 is a critical-severity improper privilege management vulnerability in github.com/fission/fission (go), affecting versions <= 1.23.0. It is fixed in 1.24.0. The application assigns, modifies, tracks, or checks privileges incorrectly, allowing a user to gain elevated access.
- How severe is CVE-2026-50564? CVE-2026-50564 has a CVSS score of 9.9 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/fission/fission are affected by CVE-2026-50564? github.com/fission/fission (go) versions <= 1.23.0 is affected.
- Is there a fix for CVE-2026-50564? Yes. CVE-2026-50564 is fixed in 1.24.0. Upgrade to this version or later.
- Is CVE-2026-50564 exploitable, and should I be worried? Whether CVE-2026-50564 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-50564 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-50564? Upgrade
github.com/fission/fissionto 1.24.0 or later.