CVE-2020-11994: Apache Camel Template Injection Vulnerability

CVE-2020-11994 Overview

CVE-2020-11994 is a Server-Side Template Injection (SSTI) vulnerability affecting Apache Camel templating components that can lead to arbitrary file disclosure. This vulnerability allows remote attackers to inject malicious template directives into Camel's templating engines, potentially enabling them to read sensitive files from the server filesystem without authentication.

Critical Impact

Remote attackers can exploit this SSTI vulnerability to read arbitrary files from vulnerable Apache Camel instances, potentially exposing configuration files, credentials, and other sensitive data.

Affected Products

• Apache Camel (multiple versions including 2.25.0 and 2.25.1)
• Oracle Communications Diameter Signaling Router
• Oracle Enterprise Manager Base Platform 13.4.0.0
• Oracle Enterprise Repository 11.1.1.7.0

Discovery Timeline

• July 8, 2020 - CVE-2020-11994 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-11994

Vulnerability Analysis

This vulnerability stems from improper input validation (CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component) within Apache Camel's templating components. When user-controllable input is passed directly to templating engines without proper sanitization, attackers can inject template directives that execute with the privileges of the Camel application.

The templating components in Apache Camel process template files using various engines (such as Velocity, FreeMarker, or Mustache). When these components accept external input that becomes part of the template evaluation context, an attacker can craft malicious payloads that break out of the intended template logic and access server-side resources.

Root Cause

The root cause of CVE-2020-11994 lies in insufficient input sanitization and improper handling of user-supplied data within Camel's templating processors. The vulnerability occurs when:

1. User input is incorporated into template expressions without proper escaping
2. Template engines evaluate the injected directives as legitimate template code
3. The resulting server-side template injection allows file system access

This injection pattern enables attackers to leverage template engine features designed for file inclusion to read arbitrary files from the server.

Attack Vector

The attack vector for this vulnerability is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by sending specially crafted requests to applications using vulnerable Camel templating components.

The attack typically follows this pattern: the attacker identifies an endpoint that processes user input through a Camel templating component, then crafts a payload containing template injection syntax specific to the underlying template engine. Once processed, the malicious template directive can instruct the engine to include and render the contents of arbitrary files, effectively disclosing sensitive server-side data to the attacker.

Since the vulnerability focuses on information disclosure (confidentiality impact), successful exploitation does not directly enable code execution but can reveal critical information such as configuration files, database credentials, API keys, and other sensitive data that could facilitate further attacks.

Detection Methods for CVE-2020-11994

Indicators of Compromise

• Unusual file access patterns in application logs, particularly attempts to read /etc/passwd, configuration files, or other sensitive paths
• HTTP requests containing template injection syntax (e.g., ${, #{, <#, {{) in unexpected parameters
• Error messages revealing template engine stack traces or file system paths
• Anomalous outbound data transfers that may indicate exfiltration of disclosed file contents

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block common SSTI payloads targeting Velocity, FreeMarker, and other template engines
• Monitor application logs for template parsing errors or file access exceptions that may indicate exploitation attempts
• Deploy runtime application self-protection (RASP) solutions to detect template injection at the application layer
• Review audit logs for access to sensitive files outside normal application behavior

Monitoring Recommendations

• Enable verbose logging on Apache Camel applications to capture all template processing activities
• Configure file integrity monitoring on sensitive configuration files and directories
• Set up alerts for unusual patterns of file read operations from Camel processes
• Monitor network traffic for responses containing unexpected file contents or system information

How to Mitigate CVE-2020-11994

Immediate Actions Required

• Upgrade Apache Camel to a patched version that addresses CVE-2020-11994
• Review all applications using Camel templating components to identify potentially vulnerable endpoints
• Implement input validation to sanitize user-supplied data before processing through template engines
• Apply the principle of least privilege to the Camel application's filesystem access

Patch Information

Apache has released patches addressing this vulnerability. Organizations should update to the latest stable version of Apache Camel. Additionally, Oracle has addressed this vulnerability in their affected products through the following security alerts:

• Oracle Security Alert January 2021
• Oracle Security Alert April 2021
• Oracle Security Alert October 2021

Review the Apache Tomcat Mailing List Announcement for additional technical details.

Workarounds

• If immediate patching is not possible, restrict network access to vulnerable Camel endpoints using firewall rules
• Implement a reverse proxy with request filtering to block suspicious template injection patterns
• Disable unused templating components in Camel configurations to reduce the attack surface
• Apply strict input validation and encoding at the application layer before data reaches templating engines

# Configuration example - Restrict file access in Camel application
# Add security manager policies to limit file system access
# Example for Java Security Manager (java.policy)
grant {
    // Restrict file read access to application directories only
    permission java.io.FilePermission "/app/templates/*", "read";
    permission java.io.FilePermission "/app/resources/*", "read";
    // Deny access to sensitive system files
    // (default deny for paths not explicitly granted)
};