The vulnerability lies in Fission’s Environment Custom Resource Definition, which exposes pod specification fields—such as hostNetwork, hostPID, hostIPC, container privileged, and serviceAccountName—to user input without validation. When an Environment object is created or updated, these fields are merged into the runtime and builder pod specs, allowing an attacker to spawn privileged or host‑level pods that can bypass normal Kubernetes isolation. This leads to full compromise of the node, giving an attacker root-level access to the underlying host machine and potentially to the entire cluster.

All installations of the Fission serverless framework running a version earlier than 1.24.0 are affected. The issue is present in every release prior to the 1.24.0 update, and any Environment CRD in those versions that contains unfiltered podSpec values is vulnerable.

The CVSS score of 9.9 classifies this as critical severity. While no EPSS score is available, the lack of a CISA KEV listing does not diminish the inherent risk; Kubernetes environments are a high-value target for attackers seeking escalation. The likely attack vector requires the ability to create or modify Environment objects, typically granted to developers or CI/CD systems; from that position an attacker can inject privileged pods, effectively escaping the node containment. This can lead to persistently compromised hosts, data exfiltration, or further lateral movement within the cluster.