Summary
Fission Environment CRD PodSpec Injection Leading to Node Escape and Cluster Takeover
A stronger framing of the same root cause as GHSA-gx55-f84r-v3r7: the Environment.spec.runtime.podSpec / spec.builder.podSpec passthrough lacked validation, and MergePodSpec propagated dangerous fields into the generated pods.
Details
Three independent flaws compounded:
- Validate gap.
pkg/apis/core/v1/validation.go::Environment.Validatechecked only container naming conventions, neverhostPID/hostIPC/hostNetwork/hostPath/privileged. - UPDATE bypass. The
pkg/webhook/environment.gokubebuilder marker registeredverbs=createonly. A tenant couldkubectl applya clean Environment and thenkubectl patchin the dangerous fields, the webhook was never called. - Merge propagation.
pkg/executor/util/merge.go::MergePodSpecunconditionally forwardedHostPID,HostIPC,HostNetwork,Volumes(including hostPath),SecurityContext, andServiceAccountNameinto the Deployments
generated by poolmgr / newdeploy / buildermgr.
A kubectl apply plus a follow-up kubectl patch caused poolmgr to schedule a privileged pod with a host-root mount within roughly 20 seconds. From that pod the cluster CA private key was readable, allowing the attacker to sign
arbitrary kubelet certificates and achieve full cluster takeover.
Duplicate handling
This advisory and GHSA-gx55-f84r-v3r7 were reported separately but close to the same code fix. Both are published to acknowledge each reporter's contribution and to keep the public CVE record clear about the multi-layer nature of the
issue.
Impact
environments.fission.io create/update RBAC is escalated to node escape and, via the readable cluster CA key, full cluster 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-2026-50545 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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See it in your environmentNew to Kodem? Get a demo →Remediation advice
Fixed in #3391 (with the companion buildermgr SA-token fix in #3390) and released in
v1.24.0. Each enumerated flaw is addressed:
- Validate,
ValidatePodSpecSafetyis called fromEnvironment.Validatefor bothRuntime.PodSpecandBuilder.PodSpec. - UPDATE bypass, the webhook marker is extended to
verbs=create;update; chart and envtest manifests are aligned. - Merge propagation, host namespaces,
ServiceAccountName, and hostPath volumes are stripped at the merge layer; per-containerprivileged/allowPrivilegeEscalationand dangerous capabilities are sanitized.
See GHSA-gx55-f84r-v3r7 for the detailed fix, both advisories close to the same commit.
Frequently Asked Questions
- What is CVE-2026-50545? CVE-2026-50545 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-2026-50545? CVE-2026-50545 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-2026-50545? github.com/fission/fission (go) versions <= 1.23.0 is affected.
- Is there a fix for CVE-2026-50545? Yes. CVE-2026-50545 is fixed in 1.24.0. Upgrade to this version or later.
- Is CVE-2026-50545 exploitable, and should I be worried? Whether CVE-2026-50545 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-2026-50545 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-2026-50545? Upgrade
github.com/fission/fissionto 1.24.0 or later.