How to Fix CVE-2026-40104: Allocation of resources without limits flaw in org.xwiki.platform:xwiki-platform-legacy-oldcore

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

What is CVE-2026-40104?

XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. Versions 1.8-rc-1, 17.0.0-rc-1 and 17.5.0-rc-1 and prior include a resource exhaustion vulnerability in REST API endpoints such as /xwiki/rest/wikis/xwiki/spaces/AnnotationCode/pages/AnnotationConfig/objects/AnnotationCode.AnnotationConfig/0/properties, which list all available pages as part of the metadata for database list properties without applying query limits. On large wikis, this can exhaust available server resources. This issue has been patched in versions 16.10.16, 17.4.8 and 17.10.1.

Am I affected?

Run the version check that matches your platform:

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

Compare what you see against the Affected row above (xwiki >= 1.8-rc-1, < 16.10.16, >= 17.0.0-rc-1, < 17.4.8, >= 17.5.0-rc-1, < 17.10.1). If your build sits inside that range, you are exposed and should patch.

How to fix CVE-2026-40104

The primary fix is to upgrade org.xwiki.platform:xwiki-platform-legacy-oldcore to the patched build. Use the commands for your platform below; the patched versions listed in the vendor advisory are: org.xwiki.platform:xwiki-platform-oldcore 16.10.16; org.xwiki.platform:xwiki-platform-oldcore 17.4.8; org.xwiki.platform:xwiki-platform-oldcore 17.10.1; org.xwiki.platform:xwiki-platform-legacy-oldcore 16.10.16 (and 2 more SKUs — see vendor advisory).

Ubuntu / Debian

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

RHEL / CentOS / Rocky / AlmaLinux

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

SUSE / openSUSE

sudo zypper patch --category security
rpm -q orgxwikiplatformxwiki

Complete PowerShell remediation script (Windows)

# Fix script for CVE-2026-40104 affecting org.xwiki.platform:xwiki-platform-legacy-oldcore
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-40104-fix-$(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 org.xwiki.platform:xwiki-platform-legacy-oldcore"
    $pkg = winget list --id "org_xwiki_platform_xwiki" 2>$null
    Write-Host $pkg

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

    Write-Host "[3/4] Applying upgrade to org.xwiki.platform:xwiki-platform-oldcore 16.10.16; org.xwiki.platform:xwiki-..."
    winget upgrade --id "org_xwiki_platform_xwiki" --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 "org_xwiki_platform_xwiki"
    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-2026-40104 affecting org.xwiki.platform:xwiki-platform-legacy-oldcore
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-40104-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 orgxwikiplatformxwiki 2>/dev/null | grep -i version || echo "orgxwikiplatformxwiki not installed via dpkg"
elif command -v rpm >/dev/null; then
    rpm -q orgxwikiplatformxwiki || echo "orgxwikiplatformxwiki not installed via rpm"
fi

echo "[2/4] Backing up configuration"
BACKUP="/root/backup-cve-2026-40104-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/orgxwikiplatformxwiki /etc/orgxwikiplatformxwiki.d /etc/orgxwikiplatformxwiki.conf; do
    [ -e "$d" ] && cp -a "$d" "$BACKUP/" || true
done

echo "[3/4] Applying upgrade (target: org.xwiki.platform:xwiki-platform-oldcore 16.10.16; org.xwiki.platform:xwiki-...)"
if command -v apt-get >/dev/null; then
    apt-get update
    apt-get install --only-upgrade -y orgxwikiplatformxwiki
elif command -v dnf >/dev/null; then
    dnf upgrade --security -y orgxwikiplatformxwiki
elif command -v yum >/dev/null; then
    yum update -y orgxwikiplatformxwiki
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 orgxwikiplatformxwiki 2>/dev/null | grep -i version
elif command -v rpm >/dev/null; then
    rpm -q orgxwikiplatformxwiki
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 orgxwikiplatformxwiki
sudo systemctl disable orgxwikiplatformxwiki

How to verify the fix worked

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

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

Expected: the reported version is at or above org.xwiki.platform:xwiki-platform-oldcore 16.10.16; org.xwiki.platform:xwiki-platform-oldcore 17.4.8; org.xwiki.platform:xwiki-platform-oldcore 17.10.1; org.xwiki.platform:xwiki-platform-legacy-oldcore 16.10.16 (and 2 more SKUs, see vendor advisory). 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

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Is CVE-2026-40104 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?

6.9 (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://github.com/xwiki/xwiki-platform/security/advisories/GHSA-mrqg-xmgm-rc5g
• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40104
• https://github.com/xwiki/xwiki-platform/commit/47b568c4753a6e682b14be1ca581bdd3b25d45a7
• https://jira.xwiki.org/browse/XWIKI-23550

*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.*