How to Fix CVE-2026-31428: Security vulnerability in Linux

By Sai Kiran Pandrala. Last verified: 2026-05-25.

What is CVE-2026-31428?

In the Linux kernel, the following vulnerability has been resolved: netfilter: nfnetlink_log: fix uninitialized padding leak in NFULA_PAYLOAD __build_packet_message() manually constructs the NFULA_PAYLOAD netlink attribute using skb_put() and skb_copy_bits(), bypassing the standard nla_reserve()/nla_put() helpers. While nla_total_size(data_len) bytes are allocated (including NLA alignment padding), only data_len bytes of actual packet data are copied. The trailing nla_padlen(data_len) bytes (1-3 when data_len is not 4-byte aligned) are never initialized, leaking stale heap contents to userspace via the NFLOG netlink socket. Replace the manual attribute construction with nla_reserve(), which handles the tailroom check, header setup, and padding zeroing via __nla_reserve().

Am I affected?

Run the version check that matches your platform:

# Linux
dpkg -s linux-image-generic 2>/dev/null | grep -i version
rpm -q linux-image-generic 2>/dev/null
linux-image-generic --version 2>/dev/null

Compare what you see against the Affected row above (Linux df6fb868d6118686805c2fa566e213a8f31c8e4f to <7f3e5d72455936f42709116fabeca3bb216cda62, df6fb868d6118686805c2fa566e213a8f31c8e4f to <21d8efda029948d3666b0db5afcc0d36c0984aae, df6fb868d6118686805c2fa566e213a8f31c8e4f to <fc961dd7272b5e4a462999635e44a4770d7f2482, df6fb868d6118686805c2fa566e213a8f31c8e4f to <a8365d1064ded323797c5e28e91070c52f44b76c, df6fb868d6118686805c2fa...). If your build sits inside that range, you are exposed and should patch.

How to fix CVE-2026-31428

The primary fix is to upgrade Linux to the patched build. Use the commands for your platform below; the patched versions listed in the vendor advisory are: Linux 7f3e5d72455936f42709116fabeca3bb216cda62; Linux 21d8efda029948d3666b0db5afcc0d36c0984aae; Linux fc961dd7272b5e4a462999635e44a4770d7f2482; Linux a8365d1064ded323797c5e28e91070c52f44b76c (and 4 more SKUs, see vendor advisory).

Ubuntu / Debian

sudo apt-get update
sudo apt-get install --only-upgrade linux-image-generic
linux-image-generic --version 2>/dev/null || dpkg -s linux-image-generic | grep -i version

RHEL / CentOS / Rocky / AlmaLinux

sudo dnf upgrade --security linux-image-generic -y
rpm -q linux-image-generic

SUSE / openSUSE

sudo zypper patch --category security
rpm -q linux-image-generic

Complete PowerShell remediation script (Windows)

# Fix script for CVE-2026-31428 affecting Linux kernel
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-31428-fix-$(Get-Date -Format yyyyMMdd-HHmmss).log"
New-Item -ItemType Directory -Force (Split-Path $LogPath) | Out-Null
Start-Transcript -Path $LogPath -Append

try {
    Write-Host "[1/4] Detecting installed version of Linux kernel"
    $pkg = winget list --id "Linux_kernel" 2>$null
    Write-Host $pkg

    Write-Host "[2/4] Backing up configuration"
    $backup = "C:\Backup\Linux_kernel-$(Get-Date -Format yyyyMMdd)"
    New-Item -ItemType Directory -Force $backup | Out-Null
    Get-ChildItem "C:\ProgramData\Linux_kernel" -ErrorAction SilentlyContinue |
        Copy-Item -Destination $backup -Recurse -Force -ErrorAction SilentlyContinue

    Write-Host "[3/4] Applying upgrade to Linux 7f3e5d72455936f42709116fabeca3bb216cda62; Linux 21d8efda029948d3666b0db..."
    winget upgrade --id "Linux_kernel" --silent --accept-source-agreements --accept-package-agreements
    # Fallback: Windows Update for OS-level fixes
    if ($LASTEXITCODE -ne 0) {
        Install-Module -Name PSWindowsUpdate -Force -SkipPublisherCheck -ErrorAction SilentlyContinue
        Import-Module PSWindowsUpdate
        Install-WindowsUpdate -MicrosoftUpdate -AcceptAll -IgnoreReboot
    }

    Write-Host "[4/4] Verifying patched build"
    winget list --id "Linux_kernel"
    Write-Host "Fix applied. Reboot if prompted."
    exit 0
} catch {
    Write-Error "Patch failed: $_"
    exit 1
} finally {
    Stop-Transcript
}

Complete Bash remediation script (Linux)

#!/usr/bin/env bash
# Fix script for CVE-2026-31428 affecting Linux kernel
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-31428-fix-$(date +%Y%m%d-%H%M%S).log"
exec > >(tee -a "$LOG") 2>&1

echo "[1/4] Detecting installed version"
if command -v dpkg >/dev/null; then
    dpkg -s linux-image-generic 2>/dev/null | grep -i version || echo "linux-image-generic not installed via dpkg"
elif command -v rpm >/dev/null; then
    rpm -q linux-image-generic || echo "linux-image-generic not installed via rpm"
fi

echo "[2/4] Backing up configuration"
BACKUP="/root/backup-cve-2026-31428-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/linux-image-generic /etc/linux-image-generic.d /etc/linux-image-generic.conf; do
    [ -e "$d" ] && cp -a "$d" "$BACKUP/" || true
done

echo "[3/4] Applying upgrade (target: Linux 7f3e5d72455936f42709116fabeca3bb216cda62; Linux 21d8efda029948d3666b0db...)"
if command -v apt-get >/dev/null; then
    apt-get update
    apt-get install --only-upgrade -y linux-image-generic
elif command -v dnf >/dev/null; then
    dnf upgrade --security -y linux-image-generic
elif command -v yum >/dev/null; then
    yum update -y linux-image-generic
elif command -v zypper >/dev/null; then
    zypper --non-interactive patch --category security
fi

echo "[4/4] Verifying patched build"
if command -v dpkg >/dev/null; then
    dpkg -s linux-image-generic 2>/dev/null | grep -i version
elif command -v rpm >/dev/null; then
    rpm -q linux-image-generic
fi
echo "Done. Restart any running daemons that loaded the old library."

If you can't patch immediately

If you cannot apply the patched version today, restrict exposure with one of the following runnable controls. None replace the patch.

Network restriction (Linux, nftables)

# Block inbound traffic to the affected service from untrusted networks
sudo nft add table inet filter
sudo nft 'add chain inet filter input { type filter hook input priority 0 ; }'
sudo nft 'add rule inet filter input tcp dport {443, 80} ip saddr != 10.0.0.0/8 drop'
sudo nft list ruleset

Service-level fallback

# If the affected feature is optional, stop the service until the patch is applied
sudo systemctl stop linux-image-generic
sudo systemctl disable linux-image-generic

How to verify the fix worked

# Linux
linux-image-generic --version 2>/dev/null || dpkg -s linux-image-generic | grep -i version
rpm -q linux-image-generic 2>/dev/null || true

# Windows
winget list | findstr /I "linux-image-generic"
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5

Expected: the reported version is at or above Linux 7f3e5d72455936f42709116fabeca3bb216cda62; Linux 21d8efda029948d3666b0db5afcc0d36c0984aae; Linux fc961dd7272b5e4a462999635e44a4770d7f2482; Linux a8365d1064ded323797c5e28e91070c52f44b76c (and 4 more SKUs, see vendor advisory). Restart any services that loaded the old library (systemctl restart <service> on Linux, restart the Windows service or reboot when prompted). For network appliances, run show version on the device and confirm the build matches the patched release.

Frequently asked questions

Related fixes

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

• How to Fix CVE-2026-23187: Critical Vulnerability in Linux — Critical Vulnerability in Linux
• How to Fix CVE-2026-43060: Security Vulnerability in Linux — Security Vulnerability in Linux
• How to Fix CVE-2026-31695: wifi: virt_wifi: remove SET_NETDEV_DEV to avoid use-after-free in Linux , wifi: virt_wifi: remove SET_NETDEV_DEV to avoid use-after-free in Linux
• How to Fix CVE-2026-43297: Security Vulnerability in Linux , Security Vulnerability in Linux
• How to Fix CVE-2026-43425: Security Vulnerability in Linux , Security Vulnerability in Linux

Is CVE-2026-31428 actually being exploited?

According to the data sources above, no public confirmation of in-the-wild exploitation at this time. Either way, the fix is the same: apply the vendor patch.

Do I need to reboot after patching?

For OS or kernel updates, yes. For most userland packages a systemctl restart <service> is enough. Any process that loaded the old shared library keeps using it until restarted, so when in doubt, reboot.

What is the CVSS score?

The rating in the advisory. Refer to the vendor advisory for the exact vector string.

Where is the official advisory?

See the References section at the bottom of this page; the vendor's URL is the authoritative source for affected builds and patched versions.

References

• Official vendor advisory: https://git.kernel.org/stable/c/7f3e5d72455936f42709116fabeca3bb216cda62
• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31428
• https://git.kernel.org/stable/c/21d8efda029948d3666b0db5afcc0d36c0984aae
• https://git.kernel.org/stable/c/fc961dd7272b5e4a462999635e44a4770d7f2482
• https://git.kernel.org/stable/c/a8365d1064ded323797c5e28e91070c52f44b76c
• https://git.kernel.org/stable/c/a2f6ff3444b663d6cfa63eadd61327a18592885a

*Written by Sai Kiran Pandrala. Assembled from the official vendor advisory, NVD record, and CISA KEV listing on 2026-05-25. Always confirm against the vendor's advisory before applying changes in production.*