How to remediate – Apache Struts Detection for Linux/UNIX

1. Introduction

The remote host contains a web application that uses Apache Struts, a Java-based MVC framework. This vulnerability indicates the presence of an application built with this framework, which may be subject to known exploits if not properly patched and configured. A successful exploit could lead to remote code execution on the server hosting the application, impacting confidentiality, integrity, and availability.

2. Technical Explanation

Apache Struts is a powerful Java MVC framework used for building web applications. This detection plugin identifies instances of Struts in default Tomcat installation directories. Exploitation typically involves sending malicious requests to the web application that trigger vulnerabilities within the Struts framework, leading to code execution on the server.

• Root cause: The presence of Apache Struts indicates a potential for known vulnerabilities if not updated.
• Exploit mechanism: Attackers exploit flaws in Struts through crafted HTTP requests that execute arbitrary code on the server.
• Scope: Web applications built with Apache Struts running on Linux/UNIX systems, specifically those installed within default or common Tomcat directories.

3. Detection and Assessment

To confirm whether a system is vulnerable, first check for the presence of Struts installations in typical locations. A thorough method involves scanning the application’s dependencies.

• Quick checks: Check for the existence of Struts JAR files within Tomcat installation directories (e.g., /opt/tomcat/webapps).
• Scanning: Use vulnerability scanners to identify known Struts vulnerabilities in deployed web applications. Example signature ID: IAVT-0001-T-0534.
• Logs and evidence: Examine application logs for errors related to Struts components or suspicious activity.

ls /opt/tomcat/webapps | grep struts

4. Solution / Remediation Steps

To fix the issue, update Apache Struts to the latest version and apply any relevant security patches.

4.1 Preparation

• Ensure you have a rollback plan in place by keeping copies of original files.
• A change window may be required depending on your environment. Approval from system owners might be needed.

4.2 Implementation

1. Step 1: Download the latest version of Apache Struts from https://struts.apache.org/.
2. Step 2: Replace existing Struts JAR files with the new versions in your web application’s classpath (e.g., within the Tomcat webapps directory).
3. Step 3: Restart the Tomcat service to apply the changes.

4.3 Config or Code Example

Before

<dependency>
  <groupId>org.apache.struts</groupId>
  <artifactId>struts2-core</artifactId>
  <version>2.3.34</version>
</dependency>

After

<dependency>
  <groupId>org.apache.struts</groupId>
  <artifactId>struts2-core</artifactId>
  <version>2.5.34</version>
</dependency>

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent issues related to vulnerable frameworks like Apache Struts. Least privilege reduces the impact of exploitation, while input validation prevents malicious data from being processed.

• Practice 1: Implement least privilege principles for application accounts and processes to limit potential damage if exploited.
• Practice 2: Enforce strict input validation on all user-supplied data to block potentially harmful requests.

4.5 Automation (Optional)

#!/bin/bash
# Example script to update Struts JAR files in Tomcat webapps directory
TOMCAT_HOME=/opt/tomcat
for app in $TOMCAT_HOME/webapps/*; do
  if [ -d "$app" ]; then
    find "$app" -name "struts*.jar" -exec rm {} ; # Remove old jars (use with caution)
    # Download and install new Struts JARs here...
  fi
done

5. Verification / Validation

• Post-fix check: Run ls /opt/tomcat/webapps | grep struts and verify that the output shows the updated Struts version.
• Re-test: Repeat the scanning process from Section 3 to confirm that no vulnerabilities are detected.
• Smoke test: Verify basic application functionality (e.g., login, data submission) to ensure the update did not introduce regressions.
• Monitoring: Monitor application logs for errors related to Struts components and set up alerts for suspicious activity.

ls /opt/tomcat/webapps | grep struts

6. Preventive Measures and Monitoring

Update security baselines to include the latest Struts version requirements. Implement checks in CI/CD pipelines to prevent deployment of vulnerable versions.

• Baselines: Update your security baseline or policy to require the use of patched Apache Struts versions.
• Pipelines: Add Static Application Security Testing (SAST) tools to your CI/CD pipeline to identify known vulnerabilities in deployed web applications.
• Asset and patch process: Establish a regular patch review cycle for all software components, including frameworks like Apache Struts.

7. Risks, Side Effects, and Roll Back

Updating Struts may introduce compatibility issues with existing application code. Keep backups of original files to facilitate roll back if necessary.

• Risk or side effect 2: Service downtime during Tomcat restart. Mitigation: Plan for a maintenance window and communicate with users.
• Roll back:
  1. Step 1: Stop the Tomcat service.
  2. Step 2: Restore the original Struts JAR files from your backup.
  3. Step 3: Restart the Tomcat service.

8. References and Resources

• Vendor advisory or bulletin: https://struts.apache.org/
• NVD or CVE entry: Not available in context.
• Product or platform documentation relevant to the fix: https://struts.apache.org/core3x/docs/