How to Fix CVE-2026-35565: Cross-site scripting in Apache Storm UI

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

What is CVE-2026-35565?

Stored Cross-Site Scripting (XSS) via Unsanitized Topology Metadata in Apache Storm UI Versions Affected: before 2.8.6 Description: The Storm UI visualization component interpolates topology metadata including component IDs, stream names, and grouping values directly into HTML via innerHTML in parseNode() and parseEdge() without sanitization at any layer. An authenticated user with topology submission rights could craft a topology containing malicious HTML/JavaScript in component identifiers (e.g., a bolt ID containing an onerror event handler). This payload flows through Nimbus → Thrift → the Visualization API → vis.js tooltip rendering, resulting in stored cross-site scripting. In multi-tenant deployments where topology submission is available to less-trusted users but the UI is accessed by operators or administrators, this enables privilege escalation through script execution in an admin's browser session.

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

# Windows
winget list | findstr /I "apache2"
Get-WmiObject Win32_Product | Where-Object { $_.Name -like "*Apache Storm UI*" } | Select-Object Name, Version

Compare what you see against the Affected row above (Apache Software Foundation Apache Storm UI 0 to <2.8.6). If your build sits inside that range, you are exposed and should patch.

How to fix CVE-2026-35565

The primary fix is to upgrade Apache Storm UI to the patched build. Use the commands for your platform below; the patched version listed in the vendor advisory is: Apache Storm UI 2.8.6.

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

Windows (PowerShell, run as administrator)

# Check installed version
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5

# Apply latest Microsoft security updates (Windows Update)
Install-Module -Name PSWindowsUpdate -Force -SkipPublisherCheck
Import-Module PSWindowsUpdate
Get-WindowsUpdate -MicrosoftUpdate
Install-WindowsUpdate -MicrosoftUpdate -AcceptAll -AutoReboot

# Or via winget for application-level patches
winget upgrade --all --accept-source-agreements --accept-package-agreements

If the affected component is a third-party application, identify the package and run:

winget upgrade --id <vendor.product>

Replace <vendor.product> with the actual winget identifier (run winget search Apache HTTP Server to find it).

Complete PowerShell remediation script (Windows)

# Fix script for CVE-2026-35565 affecting Apache HTTP Server
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-35565-fix-$(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 Storm UI 2.8.6"
    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-2026-35565 affecting Apache HTTP Server
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-35565-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-2026-35565-$(date +%Y%m%d)"
mkdir -p "$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 Storm UI 2.8.6)"
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

Windows firewall isolation

# Allow only management subnet to reach the vulnerable service
New-NetFirewallRule -DisplayName "Restrict Apache Storm UI" `
    -Direction Inbound -Action Block -RemoteAddress Any `
    -Protocol TCP -LocalPort 443
New-NetFirewallRule -DisplayName "Allow Mgmt Apache Storm UI" `
    -Direction Inbound -Action Allow -RemoteAddress 10.0.0.0/8 `
    -Protocol TCP -LocalPort 443

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 Storm UI 2.8.6. 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-2026-44417: Input Validation Flaw in Apache CXF — Input Validation Flaw in Apache CXF
• How to Fix CVE-2026-31910: SSRF Vulnerability in Apache OFBiz — SSRF Vulnerability in Apache OFBiz
• How to Fix CVE-2026-31387: Authentication Bypass in Apache OFBiz , Authentication Bypass in Apache OFBiz
• How to Fix CVE-2026-43515: Access Control Bypass in Apache Tomcat , Access Control Bypass in Apache Tomcat
• How to Fix CVE-2026-23902: CWE-863 Incorrect Authorization in Apache DolphinScheduler , CWE-863 Incorrect Authorization in Apache DolphinScheduler

Is CVE-2026-35565 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?

5.4 (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://storm.apache.org/2026/04/12/storm286-released.html
• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-35565
• http://www.openwall.com/lists/oss-security/2026/04/12/7

*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.*