The vulnerability arises from insufficient validation of the Function.spec.podspec in Fission's Container Executor. The validation only checked for the presence of podspec but did not inspect its contents. The merge logic unconditionally forwarded privileged podspec fields such as hostPID, hostNetwork, hostIPC, hostPath volumes, serviceAccountName, and privileged container flags into the deployment spec. This allowed a tenant with only functions.fission.io/create permission to craft a podspec that mounts the host root filesystem and shares host namespaces, effectively escalating privileges to node escape. The executor, running with a high-privilege service account, creates the deployment on behalf of the tenant, turning function creation into an effective deployment creation with arbitrary pod security configurations. The vulnerability is fixed in Fission v1.24.0 by adding podspec safety validation and sanitization during admission and merge.

A tenant with limited permissions (functions.fission.io/create) can escalate privileges to perform a node escape by deploying a privileged pod that shares host namespaces and mounts the host filesystem. This leads to full control over the node, compromising confidentiality, integrity, and availability of the host system and potentially the entire cluster.

This vulnerability is fixed in Fission version 1.24.0. Users should upgrade to v1.24.0 or later to receive the official fix, which adds strict validation and sanitization of the Function.spec.podspec to reject unsafe configurations. Functions specifying host namespaces, hostPath volumes, privileged containers, or serviceAccountName overrides are now rejected at admission. No additional mitigation is required if running the fixed version.