CVE-2026-50564 is a critical-severity (CVSS 9.9) Improper Privilege Management vulnerability in github.com/fission/fission. A fix is available for github.com/fission/fission — see the affected versions and patch details below.
Fission Environment CRD podspec passthrough enables hostPID/hostNetwork/privileged pods, node escape
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-50564.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-50564 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 380,066 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
github.com/fission/fissionReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/fission/fission | all versions | 1.24.0go get github.com/fission/fission@v1.24.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/fission/fission, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/fission/fission to 1.24.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-50564 is resolved across your whole dependency graph.
Workarounds
Close the privilege gap rather than the entry point: audit which accounts, roles and service identities can reach the affected operation, drop the component to the least privilege it actually needs, and review file and directory permissions created by earlier installs — a default left in place is what makes this reachable.
Frequently Asked Questions
Is CVE-2026-50564 in your dependencies?
Find it across Go, including transitive dependencies.