1. Introduction
The Apache Tomcat SendMailServlet sendmail.jsp ‘mailfrom’ parameter is vulnerable to a cross-site scripting (XSS) attack. This allows an attacker to inject malicious scripts into web pages viewed by other users, potentially stealing cookies or performing actions on their behalf. Systems running affected versions of Tomcat examples web application are at risk. A successful exploit could compromise the confidentiality, integrity and availability of user data.
2. Technical Explanation
- Root cause: Lack of input validation on the ‘mailfrom’ parameter in SendMailServlet.
- Exploit mechanism: An attacker crafts a URL containing malicious JavaScript code within the ‘mailfrom’ parameter. When another user accesses the page, the script executes. For example:
http://example.com/examples/SendMailServlet?mailfrom= - Scope: Apache Tomcat examples web application is affected.
3. Detection and Assessment
To confirm vulnerability, check if the Tomcat examples web application is deployed. Thorough assessment involves attempting to inject a simple XSS payload.
- Quick checks: Verify that the Tomcat examples web application is not running by checking for its presence in your deployed applications list or through the Tomcat manager interface.
- Scanning: Nessus plugin ID 32481 can detect this vulnerability, but results should be verified manually.
- Logs and evidence: Examine server logs for requests to
/examples/SendMailServletwith suspicious parameters.
# No specific command available - check deployed applications list.4. Solution / Remediation Steps
The recommended solution is to remove the vulnerable Tomcat examples web application.
4.1 Preparation
- Ensure you have access to the Tomcat manager interface or deployment directory. A roll back plan involves redeploying the examples application from a backup, but is not recommended.
- A change window may be required depending on your environment and risk tolerance.
4.2 Implementation
- Step 1: Undeploy the Tomcat examples web application through the Tomcat manager interface or by removing its WAR file from the deployment directory.
4.3 Config or Code Example
No config change is needed, as the solution involves removing the vulnerable application.
Before
Tomcat examples web application deployed and accessible.After
Tomcat examples web application undeployed and inaccessible.4.4 Security Practices Relevant to This Vulnerability
- Least privilege: Restricting access to the Tomcat manager interface limits who can deploy or modify applications, reducing the attack surface.
4.5 Automation (Optional)
No automation is provided as this involves removing a whole application.
5. Verification / Validation
Confirm the fix by verifying that the examples web application is no longer accessible. Attempt to access the vulnerable servlet and confirm it returns an error or does not exist.
- Post-fix check: Accessing
http://example.com/examples/SendMailServletshould return a 404 Not Found error. - Re-test: Repeat the earlier detection steps to confirm that the vulnerability is no longer present.
- Smoke test: Verify other Tomcat applications are still functioning as expected.
- Monitoring: Monitor server logs for any attempts to access the removed application.
# Accessing http://example.com/examples/SendMailServlet should return 404 Not Found.6. Preventive Measures and Monitoring
- Baselines: Implement a security baseline that prohibits deployment of example applications in production environments.
- Asset and patch process: Regularly review deployed applications and remove any unnecessary or outdated components.
7. Risks, Side Effects, and Roll Back
- Risk or side effect 1: Removing the examples application may break functionality if it is unexpectedly used by other systems.
- Roll back: Redeploying a backup of the Tomcat examples web application will restore its functionality, but also reintroduce the vulnerability. This is not recommended.
8. References and Resources
- Vendor advisory or bulletin: https://seclists.org/fulldisclosure/2007/Jul/448
- NVD or CVE entry: CVE-2007-3383
- Product or platform documentation relevant to the fix: Apache Tomcat documentation on application deployment.