How to Fix CVE-2018-19953: Cross-site Scripting (XSS) in Qts

Related fixes

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

• How to Fix CVE-2019-7194: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') — Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
• How to Fix CVE-2019-7193: Improper Input Validation in Qnap Nas Devices — Improper Input Validation in Qnap Nas Devices
• How to Fix CVE-2020-2509: Command Injection in QNAP Network-Attached Storage (NAS) , Command Injection in QNAP Network-Attached Storage (NAS)
• How to Fix CVE-2022-27593: SSRF Vulnerability in Photo Station , SSRF Vulnerability in Photo Station
• How to Fix CVE-2026-22902: Command Injection in QuNetSwitch , Command Injection in QuNetSwitch

*By Sai Kiran Pandrala*

Patch immediately. CISA's Known Exploited Vulnerabilities catalog lists this CVE, which means active exploitation has been confirmed. CISA KEV entry added 2022-05-24, federal due date 2022-06-14.

What is CVE-2018-19953?

CVE-2018-19953 is a cross-site scripting (xss) in Qts from Qnap Systems Inc.. If exploited, this cross-site scripting vulnerability could allow remote attackers to inject malicious code. QNAP has already fixed the issue in the following QTS versions. QTS 4.4.2.1231 on build 20200302; QTS 4.4.1.1201 on build 20200130; QTS 4.3.6.1218 on build 20200214; QTS 4.3.4.1190 on build 20200107; QTS 4.3.3.1161 on build 20200109; QTS 4.2.6 on build 20200109.

Why this CVE matters

This CVE sits on CISA's Known Exploited Vulnerabilities catalog, which only happens after active exploitation is observed in the wild. The cross-site scripting (xss) class of flaw gives attackers a reliable foothold against vulnerable instances of Qts. If your deployment matches the affected versions, treat any window of unpatched exposure as compromise-likely and review logs accordingly.

Am I affected?

Run the version check that matches your platform. If the installed build sits inside the affected range from the table above, the fix applies to you.

# Linux package check
dpkg -s qts 2>/dev/null | grep -i version    # Debian / Ubuntu
rpm -q qts 2>/dev/null                       # RHEL / Rocky

How to fix CVE-2018-19953

Apply the patched build the vendor names in the advisory. The commands below are starting points keyed to common platforms - adapt the package name and target version to your environment.

Ubuntu / Debian

sudo apt-get update
sudo apt-get install --only-upgrade qts
# verify the package version matches the fixed release in the advisory
dpkg -s qts | grep -i version

RHEL / CentOS / Rocky / AlmaLinux

sudo dnf upgrade --refresh qts -y
rpm -q qts

Container image

# Vendor advisory: https://www.qnap.com/zh-tw/security-advisory/qsa-20-01
# Pull the patched base image and rebuild
docker pull <your-registry>/qts:<patched-tag>
docker build -t <your-app>:patched .
docker stop <your-app> && docker rm <your-app>
docker run -d --name <your-app> <your-app>:patched

PowerShell detect/upgrade/verify/log (Windows)

# CVE-2018-19953 remediation runner — adapt the version checks to your environment.
$log = "C:\Logs\CVE-2018-19953-fix.log"
New-Item -ItemType Directory -Force -Path (Split-Path $log) | Out-Null
function Write-Log($msg) { "$(Get-Date -Format s) $msg" | Out-File $log -Append }

try {
    Write-Log "Detect: checking installed product"
    $installed = Get-CimInstance Win32_Product -ErrorAction SilentlyContinue |
        Where-Object { $_.Name -match 'QTS' }
    if (-not $installed) { Write-Log "Product not installed; nothing to do"; return }
    Write-Log "Found version $($installed.Version)"

    Write-Log "Backup: copying program files and registry hive"
    $stamp = Get-Date -Format yyyyMMdd-HHmm
    $backup = "C:\Backup\CVE-2018-19953-$stamp"
    New-Item -ItemType Directory -Force -Path $backup | Out-Null
    Copy-Item $installed.InstallLocation $backup -Recurse -ErrorAction SilentlyContinue
    reg export HKLM\Software\Microsoft\Windows\CurrentVersion\Uninstall "$backup\uninstall.reg" /y | Out-Null

    Write-Log "Upgrade: install patched build via vendor MSI / Windows Update"
    # Example MSI:  Start-Process msiexec.exe -ArgumentList '/i C:\Patches\QTS-patched.msi /qn /norestart' -Wait
    Install-WindowsUpdate -AcceptAll -AutoReboot -ErrorAction SilentlyContinue

    Write-Log "Verify: re-reading product version"
    $after = Get-CimInstance Win32_Product | Where-Object { $_.Name -match 'QTS' }
    Write-Log "Post-patch version: $($after.Version)"
    if ($after.Version -ne $installed.Version) { Write-Log "SUCCESS: version changed" } else { Write-Log "WARN: version unchanged - check vendor advisory" }
} catch {
    Write-Log "ERROR: $_"
    throw
}

Bash detect/upgrade/verify/log (Linux)

#!/usr/bin/env bash
# CVE-2018-19953 remediation runner. Re-runnable, exits non-zero on failure.
set -euo pipefail
log() { printf '%s %s\n' "$(date -Is)" "$*" | tee -a /var/log/cve-2018-19953-fix.log; }

log "Detect: current qts version"
if command -v dpkg >/dev/null 2>&1; then
    current=$(dpkg-query -W -f='${Version}' qts 2>/dev/null || echo "not-installed")
elif command -v rpm >/dev/null 2>&1; then
    current=$(rpm -q --qf '%{VERSION}-%{RELEASE}' qts 2>/dev/null || echo "not-installed")
else
    current="unknown"
fi
log "Current: $current"

log "Backup: snapshotting config"
backup="/var/backups/cve-2018-19953-$(date +%Y%m%d-%H%M)"
mkdir -p "$backup"
[ -d /etc/qts ] && cp -a /etc/qts "$backup/" || true

log "Upgrade: applying vendor patch"
if command -v apt-get >/dev/null 2>&1; then
    sudo apt-get update -qq
    sudo apt-get install -y --only-upgrade qts
elif command -v dnf >/dev/null 2>&1; then
    sudo dnf upgrade -y qts
elif command -v yum >/dev/null 2>&1; then
    sudo yum update -y qts
fi

log "Verify: re-reading qts version"
if command -v dpkg >/dev/null 2>&1; then
    after=$(dpkg-query -W -f='${Version}' qts)
else
    after=$(rpm -q --qf '%{VERSION}-%{RELEASE}' qts)
fi
log "After: $after"

if [ "$after" != "$current" ]; then
    log "SUCCESS: qts upgraded"
else
    log "WARN: version unchanged. Confirm the patched build is in your repository."
    exit 1
fi

After the upgrade, restart any service that loads the patched binary so the new code is actually running.

If you can't patch immediately

Patching is the only durable fix. These mitigations cut exposure while the change window is scheduled, they do not remove the vulnerability.

Restrict network exposure (iptables / nftables)

# Replace 10.0.0.0/8 with your management network. This drops everyone else.
sudo iptables -I INPUT -p tcp --dport 443 -s 10.0.0.0/8 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 443 -j DROP
sudo iptables-save | sudo tee /etc/iptables/rules.v4

# nftables equivalent
sudo nft add rule inet filter input tcp dport 443 ip saddr != 10.0.0.0/8 drop

How to verify the fix worked

After applying the patched build, confirm the version string matches the fixed release named in the Qnap Systems Inc. advisory.

dpkg -s qts | grep -i version       # Debian / Ubuntu
rpm -q qts                          # RHEL / Rocky

Run an authenticated vulnerability scan with a current signature set and confirm the scanner no longer flags CVE-2018-19953. For internet-facing deployments that were unpatched during the disclosure window, review logs for the affected endpoints over the full exposure period and rotate any credentials the vulnerable process could touch.

Frequently asked questions

Is CVE-2018-19953 being exploited in the wild?

Yes. CISA added CVE-2018-19953 to the Known Exploited Vulnerabilities catalog, which means active exploitation has been confirmed.

Will a firewall rule or WAF signature fully mitigate CVE-2018-19953?

No. Network-layer filters slow opportunistic scanners and block a subset of payloads, but a focused attacker who knows the bug will work around them. The vendor patch is the only durable fix.

Do I need to assume compromise if the affected service was internet-facing and unpatched?

For a CVE that CISA confirms is under active exploitation, yes. Review logs for the affected endpoints over the entire exposure window, rotate credentials the vulnerable process could read, and look for unexpected accounts, scheduled tasks, or outbound connections.

References

• Official vendor advisory: https://www.qnap.com/zh-tw/security-advisory/qsa-20-01
• NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2018-19953
• CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
• CISA KEV record: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-19953
• Additional reference: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-19953

*This guide was assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*