1. Introduction
The Apache Struts ClassLoader Manipulation vulnerability affects web applications using the Java framework Struts. This flaw allows an attacker to manipulate the ClassLoader, potentially leading to a denial of service. Systems running vulnerable versions of Struts are at risk. A successful exploit could disrupt application availability.
2. Technical Explanation
The vulnerability stems from improper handling of the ‘class’ parameter within ActionForm objects in Struts applications. An attacker can supply a malicious payload through this parameter, causing the ClassLoader to load unintended classes and ultimately leading to a denial-of-service condition. CVE-2014-0114 describes this issue. A simple example involves crafting an HTTP request with a manipulated ‘class’ parameter in an ActionForm object. Affected versions include Struts 1.
- Root cause: The vulnerability is due to insufficient input validation of the ‘class’ parameter within ActionForm objects, allowing arbitrary class loading.
- Exploit mechanism: An attacker sends a crafted HTTP request containing a malicious payload in the ‘class’ parameter of an ActionForm object. This causes Struts to load an unintended class, leading to denial of service.
- Scope: The vulnerability affects web applications using Apache Struts 1.
3. Detection and Assessment
To confirm a system is vulnerable, first check the version of Struts in use. A thorough method involves examining application dependencies for vulnerable Struts libraries.
- Quick checks: Check web application WAR files or deployment descriptors (e.g.,
web.xml) for references to Struts libraries and their versions. - Scanning: Nessus plugin ID 8458fe5f can identify vulnerable instances of Struts applications. This is an example only.
- Logs and evidence: Examine application logs for errors related to class loading or ActionForm processing.
# Example command placeholder:
# No specific command available, check WAR files directly.
4. Solution / Remediation Steps
The following steps outline how to fix the issue. Only apply these steps to systems running vulnerable versions of Struts.
4.1 Preparation
- Ensure a roll back plan is in place, including restoring backups or reverting code changes. A change window may be required depending on your environment.
4.2 Implementation
- Step 1: Upgrade Struts to the latest version if possible. Note that Struts 1 has reached end-of-life and is no longer supported, so upgrading may not be feasible.
- Step 2: If upgrading is not possible, consider disabling or removing the affected functionality within the Struts application.
4.3 Config or Code Example
Before
<action name="exampleAction" class="com.example.ExampleAction">
<form-bean type="com.example.ExampleForm"/>
After
# No direct code fix available for Struts 1, consider removing the affected action or disabling functionality.
4.4 Security Practices Relevant to This Vulnerability
Several security practices can help prevent this type of issue. Least privilege reduces impact if exploited and input validation blocks unsafe data.
- Practice 1: Implement least privilege principles, limiting the permissions granted to web applications and their components.
- Practice 2: Enforce strict input validation on all user-supplied data, including parameters passed to ActionForm objects.
4.5 Automation (Optional)
No suitable automation script is available for this specific vulnerability due to the end-of-life status of Struts 1.
5. Verification / Validation
Confirm the fix by verifying that the vulnerable functionality has been removed or disabled and re-running the earlier detection methods.
- Post-fix check: Verify that the affected action is no longer accessible or that the ‘class’ parameter is properly validated, preventing malicious payloads.
- Re-test: Re-run the Nessus scan (plugin ID 8458fe5f) to confirm that the vulnerability is no longer detected.
- Monitoring: Monitor application logs for errors related to class loading or ActionForm processing, looking for any unexpected behavior.
# Post-fix command and expected output
# No specific command available, check application accessibility directly.
6. Preventive Measures and Monitoring
Update security baselines to include checks for vulnerable Struts libraries. Add checks in CI/CD pipelines to prevent deployment of vulnerable code.
- Baselines: Update your security baseline or policy to reflect the known vulnerabilities in Apache Struts 1.
- Asset and patch process: Implement a regular review cycle for application dependencies, ensuring timely patching or mitigation of known vulnerabilities.
7. Risks, Side Effects, and Roll Back
Removing or disabling functionality may impact application features. Restore backups to roll back changes.
8. References and Resources
Link only to sources that match this exact vulnerability. Use official advisories and trusted documentation.
- Vendor advisory or bulletin: https://struts.apache.org/struts1eol-announcement.html
- NVD or CVE entry: CVE-2014-0114
- Product or platform documentation relevant to the fix: https://access.redhat.com/solutions/869353