How to Fix CVE-2026-23235: Security vulnerability in Linux

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

CVE-2026-23235 is a security vulnerability in Linux Linux. The fix is to upgrade to Linux 0; Linux 5.10.251; Linux 5.15.201; Linux 6.1.164; Linux 6.12.74; Linux 6.18.13.

What is CVE-2026-23235?

In the Linux kernel, the following vulnerability has been resolved:

f2fs: fix out-of-bounds access in sysfs attribute read/write

Some f2fs sysfs attributes suffer from out-of-bounds memory access and

incorrect handling of integer values whose size is not 4 bytes.

For example:

vm:~# echo 65537 > /sys/fs/f2fs/vde/carve_out

vm:~# cat /sys/fs/f2fs/vde/carve_out

65537

vm:~# echo 4294967297 > /sys/fs/f2fs/vde/atgc_age_threshold

vm:~# cat /sys/fs/f2fs/vde/atgc_age_threshold

1

carve_out maps to {struct f2fs_sb_info}->carve_out, which is a 8-bit

integer. However, the sysfs interface allows setting it to a value

larger than 255, resulting in an out-of-range update.

atgc_age_threshold maps to {struct atgc_management}->age_threshold,

which is a 64-bit integer, but its sysfs interface cannot correctly set

values larger than UINT_MAX.

The root causes are:

1. __sbi_store() treats all default values as unsigned int, which

prevents updating integers larger than 4 bytes and causes out-of-bounds

writes for integers smaller than 4 bytes.

1. f2fs_sbi_show() also assumes all default values are unsigned int,

leading to out-of-bounds reads and incorrect access to integers larger

than 4 bytes.

This patch introduces {struct f2fs_attr}->size to record the actual size

of the integer associated with each sysfs attribute. With this

information, sysfs read and write operations can correctly access and

update values according to their real data size, avoiding memory

corruption and truncation. The official advisory is at https://git.kernel.org/stable/c/e85a99db9ab85dfc30d93b0ca0e9156f3127f55a.

Am I affected?

Check the version of Linux you are running and compare it against the Affected row above (Linux b59d0bae6ca30c496f298881616258f9cde0d9c6 to <e85a99db9ab85dfc30d93b0ca0e9156f3127f55a; Linux b59d0bae6ca30c496f298881616258f9cde0d9c6 to <438a405fbad6882df0e34b3e1a16839a71f04240; Linux b59d0bae6ca30c496f298881616258f9cde0d9c6 to <6a6c07a9b49e43f0df42d7118fc76aa555c73d98; Linux b59d0bae6ca30c496f298881616258f9cde0d9c6 to <eebd72cff518ac87e660aefb8a41224bd88c32ce; Linux b59d0bae6ca30c496f298881616258f9cde0d9c6 to <4ef30b9f1641c9e877792df6b049f1cf507d002d; Linux b59d0bae6ca30c496f298881616258f9cde0d9c6 to <d4a594dd952df123cbdcdee9b9640d9d55e4a954). If your build sits inside the affected range, you must patch.

Run the version check that fits your platform:

# Linux package check
dpkg -s linux 2>/dev/null | grep -i ^Version
rpm -q linux 2>/dev/null
command -v linux >/dev/null && linux --version 2>/dev/null

# Windows (PowerShell)
Get-Package -Name "*Linux*" -ErrorAction SilentlyContinue | Select-Object Name, Version
winget list --name "Linux" 2>$null

How to fix CVE-2026-23235

Upgrade Linux to a patched build: Linux 0; Linux 5.10.251; Linux 5.15.201; Linux 6.1.164; Linux 6.12.74; Linux 6.18.13. The vendor advisory is the source of truth for the exact fixed version.

Ubuntu / Debian

sudo apt-get update
sudo apt-get install --only-upgrade linux
dpkg -s linux | grep -i ^Version

RHEL / CentOS / Rocky / AlmaLinux

sudo dnf upgrade --refresh linux -y
# or for older releases:
sudo yum update linux -y
rpm -q linux

SUSE / openSUSE

sudo zypper refresh
sudo zypper update linux
rpm -q linux

Node.js / npm

# Update the affected package in your project
npm install Linux@latest
npm ls Linux
npm audit fix

Complete PowerShell remediation script (Windows)

# Fix script for CVE-2026-23235 affecting Linux
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-23235-fix-$(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] Detect installed version"
    $pkg = Get-Package -Name "*Linux*" -ErrorAction SilentlyContinue
    if ($pkg) { $pkg | Format-Table Name, Version }
    else { Write-Host "Not detected via Get-Package; try winget list" }

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

    Write-Host "[3/4] Apply the upgrade to Linux 0; Linux 5.10.251; Linux 5.15.201; Linux 6.1.164; Linux 6.12.74; Linux 6.18.13"
    winget upgrade --name "Linux" --silent --accept-source-agreements --accept-package-agreements
    if ($LASTEXITCODE -ne 0) {
        # Fallback: pull latest via OS update channel
        Install-Module -Name PSWindowsUpdate -Force -SkipPublisherCheck -ErrorAction SilentlyContinue
        Import-Module PSWindowsUpdate
        Install-WindowsUpdate -MicrosoftUpdate -AcceptAll -IgnoreReboot
    }

    Write-Host "[4/4] Verify the patched build"
    winget list --name "Linux"
    Write-Host "Patch 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-2026-23235 affecting Linux
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-23235-fix-$(date +%Y%m%d-%H%M%S).log"
exec > >(tee -a "$LOG") 2>&1

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

echo "[2/4] Backup configuration"
BACKUP="/root/backup-cve-2026-23235-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/linux /etc/linux.d /etc/linux.conf; do
    [ -e "$d" ] && cp -a "$d" "$BACKUP/" || true
done

echo "[3/4] Apply the upgrade (target: Linux 0; Linux 5.10.251; Linux 5.15.201; Linux 6.1.164; Linux 6.12.74; Linux 6.18.13)"
if command -v apt-get >/dev/null; then
    apt-get update
    apt-get install --only-upgrade -y linux
elif command -v dnf >/dev/null; then
    dnf upgrade --refresh -y linux
elif command -v yum >/dev/null; then
    yum update -y linux
elif command -v zypper >/dev/null; then
    zypper --non-interactive update linux
fi

echo "[4/4] Verify the patched build"
if command -v dpkg >/dev/null; then
    dpkg -s linux 2>/dev/null | grep -i ^Version
elif command -v rpm >/dev/null; then
    rpm -q linux
fi
echo "Done. Restart any service that loaded the old library."

If you can't patch immediately

Apply at least one of the following inline controls until you can deploy the patched build. None replace the upgrade.

Restrict exposure with nftables (Linux)

# Allow only trusted CIDR to reach the affected service ports
sudo nft add table inet filter 2>/dev/null || true
sudo nft 'add chain inet filter input { type filter hook input priority 0 ; }' 2>/dev/null || true
sudo nft 'add rule inet filter input tcp dport {80, 443} ip saddr != 10.0.0.0/8 drop'
sudo nft list ruleset

Block at the host firewall (Windows)

New-NetFirewallRule -DisplayName "Block-CVE-2026-23235" -Direction Inbound -Action Block -Protocol TCP -LocalPort 80,443 -RemoteAddress Any -Enabled True
Get-NetFirewallRule -DisplayName "Block-CVE-2026-23235"

Disable the affected service (Linux)

sudo systemctl stop linux 2>/dev/null || true
sudo systemctl disable linux 2>/dev/null || true

If the vendor advisory lists an official workaround, prefer that wording verbatim. If no workaround is published, the only safe remediation is the patch.

How to verify the fix worked

After upgrading, confirm the installed version matches the patched build and that no old library is still loaded by a long-running process.

# Linux
dpkg -s linux 2>/dev/null | grep -i ^Version
rpm -q linux 2>/dev/null || true
# Pid map check for old library handles
sudo lsof +c0 2>/dev/null | grep -i "DEL.*lib" || true

# Windows
Get-Package -Name "*Linux*" | Select-Object Name, Version
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5

Expected: the reported version is at or above Linux 0; Linux 5.10.251; Linux 5.15.201; Linux 6.1.164; Linux 6.12.74; Linux 6.18.13. Restart the affected service (systemctl restart <service> on Linux, or restart the Windows service) so it loads the patched binary.

Frequently asked questions

Related fixes

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

• How to Fix CVE-2026-43200: Security Vulnerability in Linux — Security Vulnerability in Linux
• How to Fix CVE-2026-43435: Security Vulnerability in Linux — Security Vulnerability in Linux
• How to Fix CVE-2026-31602: ALSA: ctxfi: Limit PTP to a single page in Linux , ALSA: ctxfi: Limit PTP to a single page in Linux
• How to Fix CVE-2026-43243: Security Vulnerability in Linux , Security Vulnerability in Linux
• How to Fix CVE-2026-43448: Security Vulnerability in Linux , Security Vulnerability in Linux

Is CVE-2026-23235 actively exploited?

There is no public confirmation of exploitation in the wild listed in CISA KEV at the time of this writing. Patch anyway. Public exploits commonly follow disclosure within weeks.

Do I need to reboot after patching CVE-2026-23235?

For kernel and OS-level updates, yes. For most userland packages a systemctl restart <service> is enough on Linux, and restarting the Windows service or app on Windows. Any process that loaded the old library keeps using it until restarted.

What is the CVSS score for CVE-2026-23235?

Not published in the verified data we ingested. Check the NVD entry linked in the References section for the latest score.

Where is the official advisory for CVE-2026-23235?

The vendor advisory is at https://git.kernel.org/stable/c/e85a99db9ab85dfc30d93b0ca0e9156f3127f55a. The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-23235.

References

• Official vendor advisory: https://git.kernel.org/stable/c/e85a99db9ab85dfc30d93b0ca0e9156f3127f55a
• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23235
• CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
• Additional reference: https://git.kernel.org/stable/c/438a405fbad6882df0e34b3e1a16839a71f04240
• Additional reference: https://git.kernel.org/stable/c/6a6c07a9b49e43f0df42d7118fc76aa555c73d98
• Additional reference: https://git.kernel.org/stable/c/eebd72cff518ac87e660aefb8a41224bd88c32ce

*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.*