AWS patches unverified access point ownership flaw in EFS CSI Driver

Amazon Web Services released a patch for CVE-2026-85781, a vulnerability in the Amazon EFS CSI Driver that could allow unauthorized deletion of directories. The security bulletin, published on September 4, 2026, and updated on September 22, 2026, identifies a flaw in the driver’s volume-deletion logic.

The issue arises when the controller is configured with the non-default --delete-access-point-root-dir=true option. In this state, the driver failed to verify that an EFS access point referenced by a PersistentVolume’s volume handle actually belonged to the file system specified in that same handle. An authenticated Kubernetes user with permission to create PersistentVolumes could exploit this by submitting a crafted volume handle.

Context and Background

This vulnerability does not compromise Amazon EFS itself, as the service’s access controls operated as designed according to the advisory. The problem lies specifically within the open-source Kubernetes Container Storage Interface driver, which enables Kubernetes workloads to utilize Amazon EFS file systems. The flaw allowed the controller to recursively delete directories from an EFS file system that the user was not otherwise authorized to modify.

AWS credited Marcel Karlsson for collaborating on the issue through the coordinated disclosure process. The company classified the bulletin as important, requiring attention from administrators managing affected environments. The fix was incorporated into Amazon EFS CSI Driver version 3.4.1, which AWS recommends all users upgrade to immediately.

Who Is Affected

Only customers who use the --delete-access-point-root-dir option are affected by this vulnerability. Users running Amazon EFS CSI Driver version 3.4.0 or earlier are at risk if they have enabled this specific configuration. Administrators who have not enabled this option are not impacted by the flaw. AWS advises ensuring that any forked or derivative code is also patched to incorporate the new fixes included in version 3.4.1.

What should you do?

Customers who cannot upgrade to version 3.4.1 immediately should disable the --delete-access-point-root-dir option to mitigate the risk. AWS also recommends restricting PersistentVolume-creation RBAC permissions to trusted administrators only. Additionally, scoping the controller’s IAM role to manage only necessary file systems and attaching explicit EFS resource policies can reduce exposure.