How to Fix CVE-2026-33558: Deprecated: information exposure through server log in Apache Kafka

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

What is CVE-2026-33558?

Information exposure vulnerability has been identified in Apache Kafka. The NetworkClient component will output entire requests and responses information in the DEBUG log level in the logs. By default, the log level is set to INFO level. If the DEBUG level is enabled, the sensitive information will be exposed via the requests and responses output log.

Am I affected?

Run the version check that matches your platform:

# Linux
dpkg -s apache2 2>/dev/null | grep -i version
rpm -q apache2 2>/dev/null
apache2 --version 2>/dev/null

Compare what you see against the Affected row above (Apache Software Foundation Apache Kafka 0.11.0 to <3.9.1, 4.0.0; Apache Software Foundation Apache Kafka Clients 0.11.0 to <3.9.1, 4.0.0). If your build sits inside that range, you are exposed and should patch.

How to fix CVE-2026-33558

The primary fix is to upgrade Apache Kafka to the patched build. Use the commands for your platform below; the patched versions listed in the vendor advisory are: Apache Kafka 3.9.1; Apache Kafka Clients 3.9.1.

Ubuntu / Debian

sudo apt-get update
sudo apt-get install --only-upgrade apache2
apache2 --version 2>/dev/null || dpkg -s apache2 | grep -i version

RHEL / CentOS / Rocky / AlmaLinux

sudo dnf upgrade --security apache2 -y
rpm -q apache2

SUSE / openSUSE

sudo zypper patch --category security
rpm -q apache2

Complete PowerShell remediation script (Windows)

# Fix script for CVE-2026-33558 affecting Apache HTTP Server
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-33558-fix-$(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 Apache HTTP Server"
    $pkg = winget list --id "Apache_HTTP_Server" 2>$null
    Write-Host $pkg

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

    Write-Host "[3/4] Applying upgrade to Apache Kafka 3.9.1; Apache Kafka Clients 3.9.1"
    winget upgrade --id "Apache_HTTP_Server" --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 "Apache_HTTP_Server"
    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-2026-33558 affecting Apache HTTP Server
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-33558-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 apache2 2>/dev/null | grep -i version || echo "apache2 not installed via dpkg"
elif command -v rpm >/dev/null; then
    rpm -q apache2 || echo "apache2 not installed via rpm"
fi

echo "[2/4] Backing up configuration"
BACKUP="/root/backup-cve-2026-33558-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/apache2 /etc/apache2.d /etc/apache2.conf; do
    [ -e "$d" ] && cp -a "$d" "$BACKUP/" || true
done

echo "[3/4] Applying upgrade (target: Apache Kafka 3.9.1; Apache Kafka Clients 3.9.1)"
if command -v apt-get >/dev/null; then
    apt-get update
    apt-get install --only-upgrade -y apache2
elif command -v dnf >/dev/null; then
    dnf upgrade --security -y apache2
elif command -v yum >/dev/null; then
    yum update -y apache2
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 apache2 2>/dev/null | grep -i version
elif command -v rpm >/dev/null; then
    rpm -q apache2
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 apache2
sudo systemctl disable apache2

How to verify the fix worked

# Linux
apache2 --version 2>/dev/null || dpkg -s apache2 | grep -i version
rpm -q apache2 2>/dev/null || true

# Windows
winget list | findstr /I "apache2"
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5

Expected: the reported version is at or above Apache Kafka 3.9.1; Apache Kafka Clients 3.9.1. 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-2026-34538: Exposure of resource to wrong sphere in Apache Airflow — Exposure of resource to wrong sphere in Apache Airflow
• How to Fix CVE-2026-42509: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripti — Improper Neutralization of Input During Web Page Generation ('Cross-site Scripti
• How to Fix CVE-2026-24308: CWE-532 Insertion of Sensitive Information into Log File , CWE-532 Insertion of Sensitive Information into Log File
• How to Fix CVE-2026-31986: Hard-coded Credentials in Apache OFBiz , Hard-coded Credentials in Apache OFBiz
• How to Fix CVE-2026-31379: Cross-Site Scripting in Apache OFBiz , Cross-Site Scripting in Apache OFBiz

Is CVE-2026-33558 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?

5.3 (medium). 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://kafka.apache.org/cve-list
• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33558
• https://lists.apache.org/thread/pz5g4ky3h0k91tfd14p0dzqjp80960kl
• http://www.openwall.com/lists/oss-security/2026/04/17/3

*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.*