Executive brief
Fission is a framework for running serverless functions on Kubernetes. A vulnerability in how it handles function configurations allows a user with basic permissions to bypass security restrictions and run highly privileged code. This could allow an attacker to gain full control over the underlying server (node escape), potentially leading to the theft of sensitive data or a complete compromise of the cloud infrastructure.
Technical details
A vulnerability exists in Fission's Container Executor where the 'Function.spec.podspec' field is not properly validated or sanitized. Specifically, 'pkg/apis/core/v1/validation.go' fails to inspect the content of the PodSpec, and 'pkg/executor/util/merge.go' unconditionally forwards sensitive fields like 'hostPID', 'hostNetwork', and 'privileged' into the final Deployment. An attacker with 'functions.fission.io/create' permissions can submit a crafted PodSpec to mount the host root filesystem or share host namespaces. Because the executor runs with high privileges, it creates these malicious deployments on behalf of the user, leading to a container breakout and node escape. This is fixed in version 1.24.0 by implementing 'ValidatePodSpecSafety'.
Affected products
- fission fission <= 1.23.0
Timeline
- 2026-05-26: disclosed
- 2026-06-10: advisory: NVD publication date
- 2026-06-30: patched: GitHub Advisory reviewed and updated