⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● High · CVSS 8.8

How to Fix CVE-2026-28228: Server-Side Template Injection in OpenOLAT

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

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 8.8 - High
Actively exploited?Not currently listed in CISA KEV
Affected< 19.1.31, < 20.1.18, < 20.2.5
Fixed inversions
Type (CWE)CWE-1336: Improper Neutralization of Special Elements Used in a Template Engine

What is CVE-2026-28228?

CVE-2026-28228 is a server-side template injection flaw in OpenOLAT. User input is rendered as part of a template expression, which the engine then evaluates, giving the attacker code execution. Vendor description: OpenOlat is an open source web-based e-learning platform for teaching, learning, assessment and communication. Prior to versions 19.1.31, 20.1.18, and 20.2.5, an authenticated user with the Author role can inject Velocity directives into a reminder email template.

Why this CVE matters

Server-side template injection is one of the cleanest paths from web request to code execution. The vulnerable parameter is usually attacker-controlled by design, which means proof-of-concept payloads are short and reliable.

For deployments of OpenOLAT that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Even where exploitation has not been publicly observed, scanning for the vulnerable fingerprint is cheap and routine. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

Open OpenOLAT's About dialog or run the vendor-documented version-check command. Compare the result against the affected ranges in the advisory.

How to fix CVE-2026-28228

  1. Read the vendor advisory in full: https://github.com/OpenOLAT/OpenOLAT/security/advisories/GHSA-55qg-vvgj-ffh4
  2. Upgrade OpenOLAT to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  5. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

The commands below are runnable starting points. Adapt the package name, target version, and host paths to your environment using the vendor advisory linked under References.

npm / Yarn / pnpm


# Vendor advisory: https://github.com/OpenOLAT/OpenOLAT/security/advisories/GHSA-55qg-vvgj-ffh4
# Update to the patched release named in the advisory
npm install openolat@latest
# or pin to the exact fixed version from the vendor advisory
npm install openolat@<patched-version>
npm ls openolat

PyPI (pip / Poetry)


# Vendor advisory: https://github.com/OpenOLAT/OpenOLAT/security/advisories/GHSA-55qg-vvgj-ffh4
pip install --upgrade openolat
pip show openolat | grep -i version
# Poetry:
poetry add openolat@^<patched-version>

Docker / container


# Vendor advisory: https://github.com/OpenOLAT/OpenOLAT/security/advisories/GHSA-55qg-vvgj-ffh4
docker pull <your-registry>/openolat:<patched-tag>
docker stop <app> && docker rm <app>
docker run -d --name <app> <your-registry>/openolat:<patched-tag>

PowerShell detect/upgrade/verify/log (Windows)


# CVE-2026-28228 remediation runner. Adapt version checks to your environment.
$log = "C:\Logs\CVE-2026-28228-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 'OpenOLAT' }
    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
    $backup = "C:\Backup\CVE-2026-28228-$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"
    Install-WindowsUpdate -AcceptAll -AutoReboot -ErrorAction SilentlyContinue

    Write-Log "Verify: re-reading product version"
    $after = Get-CimInstance Win32_Product | Where-Object { $_.Name -match 'OpenOLAT' }
    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-2026-28228 remediation runner. Re-runnable, exits non-zero on failure.
set -euo pipefail
log() { printf '%s %s\n' "$(date -Is)" "$*" | tee -a /var/log/cve-2026-28228-fix.log; }

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

log "Backup: snapshotting config"
backup="/var/backups/cve-2026-28228-$(date +%Y%m%d-%H%M)"
mkdir -p "$backup"
[ -d /etc/openolat ] && cp -a /etc/openolat "$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 openolat
elif command -v dnf >/dev/null 2>&1; then
    sudo dnf upgrade -y openolat
elif command -v yum >/dev/null 2>&1; then
    sudo yum update -y openolat
fi

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

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

If you cannot patch immediately

Block the affected endpoint or input from untrusted users. There is no configuration-only mitigation; patch is required.

How to verify the fix worked

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for unexpected administrator accounts in OpenOLAT, scheduled tasks or cron jobs you did not create, new files in web-accessible directories, and outbound connections to addresses not in your baseline. Suspicious requests to the vulnerable endpoint immediately followed by successful 200-class responses with unusually large bodies are a strong indicator of exploitation.

Frequently asked questions

Is CVE-2026-28228 being exploited in the wild?

Public exploitation has not been confirmed by CISA at the time of writing. Treat the patch as time-sensitive anyway; reports often lag actual abuse.

Will a WAF or IDS rule fully mitigate CVE-2026-28228?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

How long should I plan for the upgrade?

Typical vendor-documented upgrade windows for OpenOLAT run from a few minutes to under an hour depending on cluster size. Test in a staging environment first and follow the vendor's documented HA upgrade order.

References

*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.*