How to Fix CVE-2026-1772: Cwe-280 improper handling of insufficient permissions or privileges in RTU500 series CMU firmware

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

CVE-2026-1772 is a cwe-280 improper handling of insufficient permissions or privileges in Hitachi Energy RTU500 series CMU firmware. The fix is to apply the vendor patch noted below.

What is CVE-2026-1772?

RTU500 web interface: An unprivileged user can read user management information. The information cannot be accessed via the RTU500 web user interface but requires further tools like browser development utilities to access them without required privileges. The CVSS base score is 5.3 (Medium). The official advisory is at https://publisher.hitachienergy.com/preview?DocumentID=8DBD000237&LanguageCode=en&DocumentPartId=&Action=Launch.

Am I affected?

Check the version of RTU500 series CMU firmware you are running and compare it against the Affected row above (RTU500 series CMU firmware 12.7.1 to <=12.7.7; RTU500 series CMU firmware 13.5.1 to <=13.5.4; RTU500 series CMU firmware 13.6.1 to <=13.6.2; RTU500 series CMU firmware 13.7.1 to <=13.7.7; RTU500 series CMU firmware 13.8.1). If your build sits inside the affected range, you must patch.

Run the version check that fits your platform:

# Linux package check
dpkg -s rtu500-series-cmu-firmware 2>/dev/null | grep -i ^Version
rpm -q rtu500-series-cmu-firmware 2>/dev/null
command -v rtu500-series-cmu-firmware >/dev/null && rtu500-series-cmu-firmware --version 2>/dev/null

# Windows (PowerShell)
Get-Package -Name "*RTU500 series CMU firmware*" -ErrorAction SilentlyContinue | Select-Object Name, Version
winget list --name "RTU500 series CMU firmware" 2>$null

How to fix CVE-2026-1772

Upgrade RTU500 series CMU firmware to a patched build: See vendor advisory. 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 rtu500-series-cmu-firmware
dpkg -s rtu500-series-cmu-firmware | grep -i ^Version

RHEL / CentOS / Rocky / AlmaLinux

sudo dnf upgrade --refresh rtu500-series-cmu-firmware -y
# or for older releases:
sudo yum update rtu500-series-cmu-firmware -y
rpm -q rtu500-series-cmu-firmware

SUSE / openSUSE

sudo zypper refresh
sudo zypper update rtu500-series-cmu-firmware
rpm -q rtu500-series-cmu-firmware

Complete PowerShell remediation script (Windows)

# Fix script for CVE-2026-1772 affecting RTU500 series CMU firmware
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-1772-fix-$(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"
    $pkg = Get-Package -Name "*RTU500 series CMU firmware*" -ErrorAction SilentlyContinue
    if ($pkg) { $pkg | Format-Table Name, Version }
    else { Write-Host "Not detected via Get-Package; try winget list" }

    Write-Host "[2/4] Backup configuration"
    $backup = "C:\Backup\rtu500-series-cmu-firmware-$(Get-Date -Format yyyyMMdd)"
    New-Item -ItemType Directory -Force $backup | Out-Null
    Get-ChildItem "C:\ProgramData\RTU500 series CMU firmware" -ErrorAction SilentlyContinue |
        Copy-Item -Destination $backup -Recurse -Force -ErrorAction SilentlyContinue

    Write-Host "[3/4] Apply the upgrade to See vendor advisory"
    winget upgrade --name "RTU500 series CMU firmware" --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 "RTU500 series CMU firmware"
    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-2026-1772 affecting RTU500 series CMU firmware
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-1772-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 rtu500-series-cmu-firmware 2>/dev/null | grep -i ^Version || echo "rtu500-series-cmu-firmware not installed via dpkg"
elif command -v rpm >/dev/null; then
    rpm -q rtu500-series-cmu-firmware || echo "rtu500-series-cmu-firmware not installed via rpm"
fi

echo "[2/4] Backup configuration"
BACKUP="/root/backup-cve-2026-1772-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/rtu500-series-cmu-firmware /etc/rtu500-series-cmu-firmware.d /etc/rtu500-series-cmu-firmware.conf; do
    [ -e "$d" ] && cp -a "$d" "$BACKUP/" || true
done

echo "[3/4] Apply the upgrade (target: See vendor advisory)"
if command -v apt-get >/dev/null; then
    apt-get update
    apt-get install --only-upgrade -y rtu500-series-cmu-firmware
elif command -v dnf >/dev/null; then
    dnf upgrade --refresh -y rtu500-series-cmu-firmware
elif command -v yum >/dev/null; then
    yum update -y rtu500-series-cmu-firmware
elif command -v zypper >/dev/null; then
    zypper --non-interactive update rtu500-series-cmu-firmware
fi

echo "[4/4] Verify the patched build"
if command -v dpkg >/dev/null; then
    dpkg -s rtu500-series-cmu-firmware 2>/dev/null | grep -i ^Version
elif command -v rpm >/dev/null; then
    rpm -q rtu500-series-cmu-firmware
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-2026-1772" -Direction Inbound -Action Block -Protocol TCP -LocalPort 80,443 -RemoteAddress Any -Enabled True
Get-NetFirewallRule -DisplayName "Block-CVE-2026-1772"

Disable the affected service (Linux)

sudo systemctl stop rtu500-series-cmu-firmware 2>/dev/null || true
sudo systemctl disable rtu500-series-cmu-firmware 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 rtu500-series-cmu-firmware 2>/dev/null | grep -i ^Version
rpm -q rtu500-series-cmu-firmware 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 "*RTU500 series CMU firmware*" | Select-Object Name, Version
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5

Expected: the reported version is at or above See vendor advisory. 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-2026-26342: Cwe-613 insufficient session expiration in Smart+ — Cwe-613 insufficient session expiration in Smart+
• How to Fix CVE-2026-20451: Access of Resource Using Incompatible Type ('Type Confusion') in MediaTek chipset — Access of Resource Using Incompatible Type ('Type Confusion') in MediaTek chipset
• How to Fix CVE-2026-35477: InvenTree (Bundle Sibling) , InvenTree (Bundle Sibling)
• How to Fix CVE-2026-25052: Critical Vulnerability in n8n , Critical Vulnerability in n8n
• How to Fix CVE-2026-35195: Out-of-bounds write in wasmtime , Out-of-bounds write in wasmtime

Is CVE-2026-1772 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-2026-1772?

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-2026-1772?

5.3 (Medium). Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N.

Where is the official advisory for CVE-2026-1772?

The vendor advisory is at https://publisher.hitachienergy.com/preview?DocumentID=8DBD000237&LanguageCode=en&DocumentPartId=&Action=Launch. The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-1772.

References

• Official vendor advisory: https://publisher.hitachienergy.com/preview?DocumentID=8DBD000237&LanguageCode=en&DocumentPartId=&Action=Launch
• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-1772
• CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog

*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.*