CVE-2026-85781 in Amazon EFS CSI Driver
Summary
by MITRE • 09/04/2026
Unverified ownership of a storage access point in the volume deletion component of the Amazon EFS CSI Driver before v3.4.1 might allow an authenticated Kubernetes user with PersistentVolume creation privileges to cause recursive deletion of directories on an EFS filesystem they are not authorized to access, via a crafted PersistentVolume volumeHandle that pairs an access point from one filesystem with a different target filesystem.
To remediate this issue, users should upgrade to version v3.4.1.
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Analysis
by VulDB Data Team • 09/04/2026
The vulnerability identified in the Amazon EFS CSI Driver prior to version 3.4.1 represents a critical authorization bypass within the storage management layer of Kubernetes environments utilizing Elastic File System resources. This flaw specifically resides in the volume deletion component, where the driver fails to adequately verify that the access point associated with a PersistentVolume actually belongs to the target filesystem specified for deletion operations. In standard AWS architecture, an EFS Access Point is tightly coupled to a specific file system and enforces POSIX permissions and path restrictions defined at its creation. However, due to this validation gap, the driver accepts a volumeHandle that incorrectly pairs an access point from one EFS filesystem with a different target filesystem identifier during deletion requests. This architectural inconsistency allows for a scenario where the operational logic proceeds based on the mismatched identifiers rather than enforcing strict ownership verification between the access point and the file system resource it is intended to manage.
From a technical perspective, this flaw constitutes an insecure direct object reference combined with insufficient validation of user-supplied input within the control plane components of the CSI driver. An authenticated Kubernetes user possessing privileges to create PersistentVolumes can exploit this logic error by crafting a volumeHandle that references an access point they do not own or have permission to use on their designated filesystem, but which exists and is accessible under different credentials or contexts elsewhere in the AWS account. When the deletion process initiates, the driver utilizes the provided access point configuration rather than validating its lineage against the target file system's metadata. Consequently, if the attacker controls the access point referenced in the crafted volume handle, they can trigger recursive directory deletions on an EFS filesystem that is otherwise outside their authorized scope of access. This effectively bypasses AWS IAM policies and EFS Access Point restrictions because the driver acts as a privileged intermediary executing commands based on flawed trust assumptions about resource ownership.
The operational impact of this vulnerability is severe, primarily centering on data integrity and availability risks within multi-tenant Kubernetes clusters or shared cloud environments. An attacker with moderate privileges can escalate their influence to cause destructive actions against critical storage assets belonging to other tenants or system components. The ability to recursively delete directories means that sensitive data stored in the target EFS filesystem could be permanently lost, leading to significant service disruptions and potential compliance violations depending on the nature of the affected data. Furthermore, this vulnerability undermines the principle of least privilege by allowing a user with limited storage creation rights to exert destructive control over unrelated infrastructure resources. The lack of proper separation between access point ownership and file system targeting creates a dangerous attack vector that compromises the isolation guarantees expected in containerized orchestration platforms.
To mitigate this risk, organizations must immediately upgrade the Amazon EFS CSI Driver to version 3.4.1 or later, where the validation logic has been corrected to ensure strict verification of storage access point ownership relative to the target filesystem before executing deletion operations. In addition to upgrading, administrators should review IAM policies and Kubernetes RBAC rules to restrict PersistentVolume creation privileges to only those users who strictly require them, thereby reducing the attack surface available for crafting malicious volume handles. Implementing rigorous monitoring on EFS API calls related to directory deletions can also aid in detecting anomalous activity indicative of exploitation attempts while remediation efforts are underway. This issue is categorized under CWE-284 Improper Access Control and aligns with ATT&CK techniques involving privilege escalation and resource hijacking, highlighting the necessity for robust input validation in cloud-native storage drivers to maintain secure multi-tenancy boundaries.