● High · CVSS 7.8

How to Fix CVE-2026-23239: espintcp: Fix race condition in espintcp_close() in Linux

Q: Is CVE-2026-23239 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-2026-23239?

CVSS rates it 7.8 (High). Use that score to set your patch priority next to the other items in your queue.

Q: Do I have to take Linux 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-2026-23239 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-2026-23273: Critical Vulnerability in Linux — Critical Vulnerability in Linux
How to Fix CVE-2026-43144: Security Vulnerability in Linux — Security Vulnerability in Linux
How to Fix CVE-2026-22986: Critical Vulnerability in Linux , Critical Vulnerability in Linux
How to Fix CVE-2026-23207: Critical Vulnerability in Linux , Critical Vulnerability in Linux
How to Fix CVE-2026-23196: Critical Vulnerability in Linux , Critical Vulnerability in Linux

*By Sai Kiran Pandrala*

⚡ At a glance


Severity	CVSS 7.8, High
Actively exploited?	No
Affected	Linux (e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 < f7ad8b1d0e421c524604d5076b73232093490d5c, e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 < 664e9df53226b4505a0894817ecad2c610ab11d8, e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 < 022ff7f347588de6e17879a1da6019647b21321b); Linux (5.6, 0 < 5.6, 6.12.75 <= 6.12.*)
Fixed in	664e9df53226b4505a0894817ecad2c610ab11d8, 022ff7f347588de6e17879a1da6019647b21321b, 5.6
Type (CWE)	Not verified

What is CVE-2026-23239?

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

espintcp: Fix race condition in espintcp_close()

This issue was discovered during a code audit. After cancel_work_sync() is called from espintcp_close(),

espintcp_tx_work() can still be scheduled from paths such as

the Delayed ACK handler or ksoftirqd. As a result, the espintcp_tx_work() worker may dereference a

freed espintcp ctx or sk.

In practical terms, a successful attacker gets exploitation of a race condition that can corrupt memory or state. 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 Linux 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 linux   # Debian/Ubuntu
rpm -qa | grep -i linux   # RHEL/CentOS/Rocky

How to fix CVE-2026-23239

The primary fix is to upgrade to the patched build listed in the Fixed in row above (664e9df53226b4505a0894817ecad2c610ab11d8, 022ff7f347588de6e17879a1da6019647b21321b, 5.6). Pick the platform that matches your install and run the commands below.

Linux (Ubuntu / Debian)


sudo apt-get update
sudo apt-get install --only-upgrade linux
# Confirm the installed version meets or exceeds 664e9df53226b4505a0894817ecad2c610ab11d8
dpkg -s linux | grep ^Version

Linux (RHEL / CentOS / Rocky)


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

Windows (PowerShell, admin)


# Try winget first
winget upgrade --id 'Linux.Linux' --silent --accept-source-agreements --accept-package-agreements
# If winget does not know the product, download the patched installer from the vendor and:
Start-Process -FilePath "$env:TEMP\Linux-664e9df53226b4505a0894817ecad2c610ab11d8.msi" -ArgumentList '/qn /norestart' -Wait

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


# Run as Administrator
$ErrorActionPreference = 'Stop'
$log = "$env:ProgramData\Linux-Patch-CVE-2026-23239.log"
function Write-Log($msg) { "$(Get-Date -Format s)  $msg" | Tee-Object -FilePath $log -Append }

Write-Log "Starting CVE-2026-23239 remediation for Linux Linux"

# 1. Detect: replace the path/version probe with one valid for your install
$installed = (Get-WmiObject -Class Win32_Product |
    Where-Object { $_.Name -like '*Linux*' } |
    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]'664e9df53226b4505a0894817ecad2c610ab11d8') {
    Write-Log "Already at fixed version $installed; no action needed."
    return
}

# 2. Backup configuration to a timestamped folder
$backup = "$env:ProgramData\Linux-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\Linux\Linux"
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\Linux-664e9df53226b4505a0894817ecad2c610ab11d8.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 { $_.Name -like '*Linux*' } |
    Select-Object -First 1 -ExpandProperty Version)
if ([version]$verify -ge [version]'664e9df53226b4505a0894817ecad2c610ab11d8') {
    Write-Log "SUCCESS: now at $verify (>= 664e9df53226b4505a0894817ecad2c610ab11d8)"
} 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/linux-patch-cve-2026-23239.log
log()  { echo "$(date -Iseconds)  $*" | tee -a "$LOG"; }

log "Starting CVE-2026-23239 remediation for Linux Linux"

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

# 2. Backup config
BACKUP=/var/backups/linux-$(date +%Y%m%d-%H%M)
mkdir -p "$BACKUP"
for d in /etc/linux /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 linux
else
    sudo dnf upgrade --security -y linux
fi

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

# Optionally compare against 664e9df53226b4505a0894817ecad2c610ab11d8 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.

No official vendor workaround is published for this CVE; patching is the only documented fix. The runnable hardening below is generic defense in depth, not a substitute for the patch.

Restrict the affected service to trusted networks (Linux):


# Vendor advisory: https://git.kernel.org/stable/c/f7ad8b1d0e421c524604d5076b73232093490d5c
# Replace <port> with the affected service port and 10.0.0.0/24 with your admin subnet
sudo iptables -A INPUT -p tcp --dport <port> -s 10.0.0.0/24 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport <port> -j DROP

Windows Firewall equivalent:


# Vendor advisory: https://git.kernel.org/stable/c/f7ad8b1d0e421c524604d5076b73232093490d5c
New-NetFirewallRule -DisplayName 'Allow affected service from admin subnet' \
    -Direction Inbound -Action Allow -Protocol TCP -LocalPort <port> -RemoteAddress 10.0.0.0/24
New-NetFirewallRule -DisplayName 'Block affected service from everywhere else' \
    -Direction Inbound -Action Block -Protocol TCP -LocalPort <port>

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 "linux"   # Debian/Ubuntu
rpm -qa | grep -i "linux"   # RHEL/CentOS/Rocky

Expected output: the package version should meet or exceed 664e9df53226b4505a0894817ecad2c610ab11d8.

Then re-run any vulnerability scanner you used previously and confirm the finding for CVE-2026-23239 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-2026-23239 being actively exploited?