Kubernetes NFS CSI flaw discovered
A critical vulnerability in the Kubernetes NFS CSI driver allows unauthorized directory deletion and modification — a storage‑layer risk that can devastate stateful workloads. Patching, policy enforcement, and runtime storage controls are urgent for clusters hosting VM and AI data. (gbhackers.com)
CVE-2026-3864 was assigned to the NFS CSI driver and posted as a Kubernetes security advisory on March 17, 2026 with a CVSS v3.1 score of 6.5 (Medium). (discuss.kubernetes.io) (discuss.kubernetes.io) The flaw is a path‑traversal bug caused by insufficient validation of the subDir/volumeHandle field, allowing sequences like “../” to escape the intended subdirectory during cleanup operations. (github.com) (github.com) All upstream CSI Driver for NFS releases prior to the v4.13.1 fix are listed as vulnerable, and the maintainers released v4.13.1 as the patched version. (discuss.kubernetes.io) (discuss.kubernetes.io) Exploitation requires the ability to create a PersistentVolume that references the nfs.csi.k8s.io driver (the CVSS vector includes PR:H, i.e., high privileges to create PVs). (github.com) (github.com) Detection guidance published with the advisory includes inspecting PersistentVolumes’ volumeHandle fields for “../” traversal sequences and scanning CSI controller logs for entries like “Removing subPath: /tmp/mount-uuid/legitimate/../../../exports/subdir”. (discuss.kubernetes.io) (discuss.kubernetes.io) The issue was reported by Shaul Ben Hai, Senior Staff Security Researcher at SentinelOne, and the fix and advisory were coordinated by the CSI Driver for NFS maintainers and the Kubernetes Security Response Committee; recommended mitigations are immediate upgrade to v4.13.1+, restricting PV creation to trusted administrators, and tightening NFS export write permissions. (discuss.kubernetes.io) (discuss.kubernetes.io)
