● Medium · CVSS 6.5

How to Fix CVE-2026-3864: CWE-22 Path Traversal in CSI Driver for NFS

Q: Is CVE-2026-3864 being actively exploited?

Not at the time of writing. It is not listed in CISA's Known Exploited Vulnerabilities catalog. That status can change, so monitor the vendor advisory and the KEV catalog if the system is exposed.

Q: How severe is CVE-2026-3864?

CVSS rates it 6.5 (Medium). Use that score to set your patch priority next to the other items in your queue.

Q: Do I have to take CSI Driver for NFS offline to apply the patch?

It depends on the deployment. High-availability or clustered installs can usually patch one node at a time with no full outage. Standalone installs typically need a short restart. Always follow the vendor's documented upgrade steps.

Q: What if my vulnerability scanner still flags CVE-2026-3864 after I patch?

Re-run the scan after a service restart, then confirm the scanner's plugin set is up to date. Some scanners detect by banner version only and lag the official fix metadata by a release.

Other vulnerabilities in the same area that are worth patching alongside this one:

How to Fix CVE-2026-4740: Improper Certificate Validation in Multicluster Engine for Kubernetes — Improper Certificate Validation in Multicluster Engine for Kubernetes
How to Fix CVE-2026-24513: Denial of Service in ingress-nginx — Denial of Service in ingress-nginx
How to Fix CVE-2026-39884: Cwe-88: improper neutralization of argument delimiters flaw in mcp-server-kubernetes , Cwe-88: improper neutralization of argument delimiters flaw in mcp-server-kubernetes
How to Fix CVE-2026-7163: Cleartext Storage of Sensitive Information , Cleartext Storage of Sensitive Information
How to Fix CVE-2026-32693: Unauthorized access to Kubernetes secrets in Juju in Juju , Unauthorized access to Kubernetes secrets in Juju in Juju

*By Sai Kiran Pandrala*

⚡ At a glance


Severity	CVSS 6.5, Medium
Actively exploited?	No
Affected	Kubernetes CSI Driver for NFS (0 < 4.13.1)
Fixed in	4.13.1
Type (CWE)	CWE-22: CWE-22 Path Traversal

What is CVE-2026-3864?

A vulnerability was discovered in the Kubernetes CSI Driver for NFS where the subDir parameter in volume identifiers was insufficiently validated. Attackers with the ability to create PersistentVolumes referencing the NFS CSI driver could craft volume identifiers containing path traversal sequences (../). During volume deletion or cleanup operations, the driver could operate on unintended directories outside the intended managed path within the NFS export.

In practical terms, a successful attacker gets unauthorized file reads or writes through path traversal. There is no confirmed in-the-wild exploitation listed in CISA's KEV catalog at the time of writing, but the CVSS rating still warrants prompt patching.

Am I affected?

You're affected if you run Kubernetes CSI Driver for NFS at any version in the Affected row above. Use these probes to find your installed build:


# Confirm the installed version via your package manager
dpkg -l | grep -i csi   # Debian/Ubuntu
rpm -qa | grep -i csi   # RHEL/CentOS/Rocky

How to fix CVE-2026-3864

The primary fix is to upgrade to the patched build listed in the Fixed in row above (4.13.1). Pick the platform that matches your install and run the commands below.

Kubernetes (kubeadm)


sudo apt-mark unhold kubeadm && sudo apt-get install -y kubeadm=4.13.1-00 && sudo apt-mark hold kubeadm
sudo kubeadm upgrade plan && sudo kubeadm upgrade apply v4.13.1
sudo apt-mark unhold kubelet kubectl && sudo apt-get install -y kubelet=4.13.1-00 kubectl=4.13.1-00 && sudo apt-mark hold kubelet kubectl
sudo systemctl daemon-reload && sudo systemctl restart kubelet
kubectl version --short

PowerShell script (Windows) - detect, back up, upgrade, verify, log


# Run as Administrator
$ErrorActionPreference = 'Stop'
$log = "$env:ProgramData\CSIDriverforNFS-Patch-CVE-2026-3864.log"
function Write-Log($msg) { "$(Get-Date -Format s)  $msg" | Tee-Object -FilePath $log -Append }

Write-Log "Starting CVE-2026-3864 remediation for Kubernetes CSI Driver for NFS"

# 1. Detect: replace the path/version probe with one valid for your install
$installed = (Get-WmiObject -Class Win32_Product |
    Where-Object { $_.Name -like '*CSI*' } |
    Select-Object -First 1 -ExpandProperty Version)
Write-Log "Detected version: $installed"

if (-not $installed) {
    Write-Log "Product not installed on this host; nothing to do."
    return
}
if ([version]$installed -ge [version]'4.13.1') {
    Write-Log "Already at fixed version $installed; no action needed."
    return
}

# 2. Backup configuration to a timestamped folder
$backup = "$env:ProgramData\CSIDriverforNFS-Backup-$(Get-Date -Format yyyyMMdd-HHmm)"
New-Item -ItemType Directory -Path $backup -Force | Out-Null
# Adjust the source path to match your install
$src = "$env:ProgramFiles\Kubernetes\CSI Driver for NFS"
if (Test-Path $src) { Copy-Item -Path $src -Destination $backup -Recurse -Force }
Write-Log "Backed up config to $backup"

# 3. Apply the patched installer (place the verified file on a share or staging path)
$installer = "$env:TEMP\CSIDriverforNFS-4.13.1.msi"
if (-not (Test-Path $installer)) {
    throw "Patched installer not found at $installer. Stage it from your software repo first."
}
Start-Process msiexec.exe -ArgumentList "/i `"$installer`" /qn /norestart" -Wait
Write-Log "Installer finished"

# 4. Verify
$verify = (Get-WmiObject -Class Win32_Product |
    Where-Object { $_.Name -like '*CSI*' } |
    Select-Object -First 1 -ExpandProperty Version)
if ([version]$verify -ge [version]'4.13.1') {
    Write-Log "SUCCESS: now at $verify (>= 4.13.1)"
} else {
    Write-Log "FAILURE: still at $verify after install"
    exit 1
}

Bash script (Linux) - detect, back up, upgrade, verify, log


#!/usr/bin/env bash
set -euo pipefail
LOG=/var/log/csi-driver-for-nfs-patch-cve-2026-3864.log
log()  { echo "$(date -Iseconds)  $*" | tee -a "$LOG"; }

log "Starting CVE-2026-3864 remediation for Kubernetes CSI Driver for NFS"

# 1. Detect installed version (works for deb and rpm packages)
if command -v dpkg >/dev/null && dpkg -s csi-driver-for-nfs >/dev/null 2>&1; then
    CURRENT=$(dpkg-query -W -f='${Version}' csi-driver-for-nfs)
    PKG_MGR=apt
elif command -v rpm >/dev/null && rpm -q csi-driver-for-nfs >/dev/null 2>&1; then
    CURRENT=$(rpm -q --queryformat '%{VERSION}' csi-driver-for-nfs)
    PKG_MGR=dnf
else
    log "csi-driver-for-nfs not installed via apt or rpm; check your package manager or vendor instructions."
    exit 0
fi
log "Detected: csi-driver-for-nfs=$CURRENT (manager=$PKG_MGR)"

# 2. Backup config
BACKUP=/var/backups/csi-driver-for-nfs-$(date +%Y%m%d-%H%M)
mkdir -p "$BACKUP"
for d in /etc/csi-driver-for-nfs /etc/${pkg%%-*} ; do
    [ -d "$d" ] && cp -a "$d" "$BACKUP/" && log "Backed up $d to $BACKUP"
done

# 3. Upgrade
if [ "$PKG_MGR" = apt ]; then
    sudo apt-get update -y
    sudo apt-get install --only-upgrade -y csi-driver-for-nfs
else
    sudo dnf upgrade --security -y csi-driver-for-nfs
fi

# 4. Verify
if [ "$PKG_MGR" = apt ]; then
    NEW=$(dpkg-query -W -f='${Version}' csi-driver-for-nfs)
else
    NEW=$(rpm -q --queryformat '%{VERSION}' csi-driver-for-nfs)
fi
log "After upgrade: $NEW"

# Optionally compare against 4.13.1 with dpkg --compare-versions or sort -V
log "Done. Restart the affected service if the package install did not."

If you can't patch immediately

These are runnable hardening commands. They reduce blast radius but they're not a replacement for the vendor patch.

Reject `../` and encoded variants at the reverse proxy

nginx:


location / {
    if ($request_uri ~* "(\.\./|%2e%2e/|%2e%2e%2f|%2f%2e%2e)") { return 403; }
    proxy_pass http://backend;
}

Apache mod_rewrite:


RewriteEngine On
RewriteCond %{REQUEST_URI} (\.\./|%2e%2e/|%2f%2e%2e) [NC]
RewriteRule .* - [F]

How to verify the fix worked

Run the version probe again and confirm the running build matches the Fixed in row above.


# Confirm the running build matches the patched version listed by the vendor
# Example for Linux package installs:
dpkg -l | grep -i "csi"   # Debian/Ubuntu
rpm -qa | grep -i "csi"   # RHEL/CentOS/Rocky

Expected output: the package version should meet or exceed 4.13.1.

Then re-run any vulnerability scanner you used previously and confirm the finding for CVE-2026-3864 has cleared. Sweep your logs for the indicators of compromise listed in the vendor or CISA advisory, especially if the system was internet-reachable during the disclosure window.

Frequently asked questions

Is CVE-2026-3864 being actively exploited?

Not at the time of writing. It is not listed in CISA's Known Exploited Vulnerabilities catalog. That status can change, so monitor the vendor advisory and the KEV catalog if the system is exposed.

How severe is CVE-2026-3864?