oss-security - [kubernetes] CVE-2026-3864: CSI Driver for NFS path traversal via subDir may delete unintended directories on the NFS server

Follow @Openwall on Twitter for new release announcements and other news

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <CAL7+V1xz3=zwKmE3TzZg64NLsFJO16q6ecqFyWdM+oWP7=etZg@mail.gmail.com>
Date: Mon, 16 Mar 2026 23:04:40 -0700
From: Rita Zhang <rita.z.zhang@...il.com>
To: oss-security@...ts.openwall.com
Subject: [kubernetes] CVE-2026-3864: CSI Driver for NFS path traversal via
 subDir may delete unintended directories on the NFS server

Hello Kubernetes Community,

A vulnerability was identified in the Kubernetes CSI Driver for NFS where
insufficient validation of the subDir parameter in volume identifiers could
allow path traversal. A malicious user with the ability to create a
PersistentVolume referencing the NFS CSI driver could craft a volumeHandle
containing traversal sequences (for example ../). When the driver performs
cleanup operations during volume deletion, these sequences may cause the
driver to operate on unintended directories on the NFS server.

An attacker exploiting this flaw could cause deletion or modification of
directories outside the intended managed subdirectory within the NFS export.

This issue has been rated Medium (6.5) with
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H
<https://www.first.org/cvss/calculator/3-1#CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H>
and assigned CVE-2026-3864.

Am I vulnerable?

You may be vulnerable if:

   -

   You run the CSI Driver for NFS (nfs.csi.k8s.io)
   -

   Your cluster allows users to create PersistentVolumes referencing the
   NFS CSI driver
   -

   Your CSI driver version does not validate traversal sequences in the
   subDir field

Affected Versions

   -

   All versions of the CSI Driver for NFS prior to the v4.13.1 release
   containing the fix for traversal validation are affected.

How do I mitigate this vulnerability?

This issue can be mitigated by:

   -

   Upgrading the CSI Driver for NFS to a patched version
   -

   Restricting PersistentVolume creation privileges to trusted
   administrators
   -

   Reviewing NFS exports to ensure only intended directories are writable
   by the driver

As a best practice, untrusted users should not be granted permission to
create arbitrary PersistentVolumes referencing external storage drivers.

Fixed Versions

   -

   CSI Driver for NFS versions >= v4.13.1

Detection

To determine if your cluster may be affected:

   -

   Inspect PersistentVolumes using the NFS CSI driver and review the
   volumeHandle field.
   -

   Look for traversal sequences such as: `../`
   -

   Review CSI controller logs for unexpected directory operations. e.g.
   “Removing subPath: /tmp/mount-uuid/legitimate/../../../exports/subdir”

If you find evidence that this vulnerability has been exploited, please
contact security@...ernetes.io

Thank You,

Rita Zhang on behalf of the Kubernetes Security Response Committee

Additional Details

See the GitHub issue for more details:
https://github.com/kubernetes/kubernetes/issues/137797

Acknowledgements

This vulnerability was reported by @Shaul Ben Hai, Senior Staff Security
Researcher from SentinelOne.

The issue was fixed by the CSI Driver for NFS maintainers and the
Kubernetes Security Response Committee.

Andy Zhang @andyzhangx

Rita Zhang @ritazh

Thank You,

Rita Zhang on behalf of the Kubernetes Security Response Committee

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.