Fission, an open‑source, Kubernetes‑native serverless platform, enforces that a function’s referenced secrets and config maps belong to the same namespace as the function. However, it mistakenly does not perform this check for environment references. An attacker who can create or modify a function can specify an EnvironmentRef that points to an environment in another namespace, allowing the function to access resources such as secrets or config maps owned by that other namespace. This flaw is classified as CWE‑284 (Improper Access Control) and CWE‑863 (Unexpected Restriction of Operations).

The affected product is Fission, version 1.23.x and earlier. The issue was addressed in release 1.24.0, which added the missing namespace validation for EnvironmentRef objects. All installations running any pre‑1.24.0 version are vulnerable.

The CVSS score is 8.5, indicating a high severity impact. No EPSS score is available and the vulnerability is not listed in CISA’s KEV catalog. The likely attack vector involves an attacker with permissions to create or update Functions, or compromise the admission webhook, who supplies an EnvironmentRef that spans namespaces. By doing so, the attacker can read or use sensitive data from the target namespace, potentially enabling further lateral movement or privilege escalation within the cluster. The exploit is straightforward once the attacker can alter function definitions.