Executive brief
Fission is a framework for serverless functions on Kubernetes. A security flaw allowed users with basic permissions to create malicious configurations that bypass standard security boundaries. An attacker could use this to escape their isolated environment, gain full control over the underlying server (node), and potentially compromise the entire data center or cloud cluster.
Technical details
The Fission Environment Custom Resource Definition (CRD) improperly handled 'spec.runtime.podSpec' and 'spec.builder.podSpec' fields, merging them into Kubernetes pod specs without validation or filtering. An attacker with 'create' or 'update' RBAC permissions on 'environments.fission.io' could inject dangerous fields such as 'hostNetwork', 'hostPID', 'hostIPC', and 'privileged: true'. Because Fission-managed namespaces lacked Pod Security Admission enforcement, these pods were successfully scheduled. This allows an attacker to use 'nsenter' to escape to the host, access cloud-metadata credentials, and achieve full node compromise. The fix in v1.24.0 introduces an admission denylist and sanitization at the merge layer.
Affected products
- fission fission <= 1.23.0
Timeline
- 2026-05-26: disclosed
- 2026-06-10: advisory: NVD publication
- 2026-06-30: patched: GitHub Advisory published/updated with fix details