How to remediate – Multi-Threaded HTTP Server v1.1 for Zimbra

1. Introduction

Multi-Threaded HTTP Server v1.1 for Zimbra is a third-party web server add-on affected by directory traversal vulnerabilities. This means an attacker could potentially view files on the system it’s running on without needing to log in. Businesses using Zimbra with this add-on enabled are at risk, particularly those exposing the server directly to the internet. A successful attack could lead to confidential data disclosure.

2. Technical Explanation

The Multi-Threaded HTTP Server for Zimbra does not properly check user input when handling URLs. This allows attackers to craft malicious requests that access files outside of the intended web directory. An unauthenticated attacker can exploit this flaw to read arbitrary files on the server’s filesystem.

• Root cause: Insufficient URL sanitisation in the HTTP request handler.
• Exploit mechanism: Attackers send a specially crafted HTTP GET request with a path traversal sequence (e.g., ‘../..’) in the URL to access files outside of the web root directory. For example, requesting /../../etc/passwd could reveal system user account information.
• Scope: Multi-Threaded HTTP Server v1.1 for Zimbra is affected. Specific versions were not provided.

3. Detection and Assessment

Confirming the presence of this server component is the first step in assessing vulnerability. Then, test access to sensitive files.

• Quick checks: Use netstat -tulnp | grep to identify processes listening on ports used by Multi-Threaded HTTP Server for Zimbra. Replace `` with the port you suspect is in use.
• Scanning: Nessus plugin ID 12304 may detect this vulnerability, but results should be verified manually.
• Logs and evidence: Check web server access logs for unusual requests containing path traversal sequences (e.g., ‘../..’). Log locations vary depending on the Zimbra configuration.

netstat -tulnp | grep 8080

4. Solution / Remediation Steps

The best approach is to either restrict access or disable this component.

4.1 Preparation

• Dependencies: None known. Roll back plan is to restore from snapshot/backup or restart the Zimbra service.
• Change window: Standard change control procedures apply for production systems. Approval may be required by security and system owners.

4.2 Implementation

1. Step 1: Limit incoming traffic to the Multi-Threaded HTTP Server for Zimbra port using a firewall rule. For example, allow access only from trusted internal networks.
2. Step 2: If the server is not required, disable it within the Zimbra configuration. Consult the Zimbra documentation for specific instructions.

4.3 Config or Code Example

Before

# No firewall rule restricting access to port 8080 (example)

After

# Firewall rule allowing access to port 8080 only from trusted networks (example - iptables)
iptables -A INPUT -p tcp --dport 8080 -s /24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this type of issue.

• Practice 1: Least privilege – restrict access to services and data based on need, reducing the impact if exploited.
• Practice 2: Input validation – always validate user input to block malicious characters or sequences like path traversal attempts.

4.5 Automation (Optional)

# Example Ansible playbook snippet to block access via firewall
- name: Block Multi-Threaded HTTP Server port
  firewalld:
    port: 8080/tcp
    permanent: true
    state: disabled
    immediate: yes

5. Verification / Validation

Confirm the fix by checking firewall rules and attempting to access sensitive files.

• Post-fix check: Use netstat -tulnp | grep again to confirm the server is listening, then use a web browser or curl to attempt to access a file outside of the web root (e.g., http:///../../etc/passwd). You should receive an error message indicating access denied.
• Re-test: Repeat the initial detection steps – scanning and log analysis – to confirm no longer vulnerable.
• Monitoring: Monitor web server access logs for failed requests containing path traversal sequences as an early warning indicator of potential attacks.

curl http:///../../etc/passwd -I

6. Preventive Measures and Monitoring

Regular security assessments and patching are key to preventing these issues.

• Baselines: Update your server baseline configuration to include firewall rules restricting access to unnecessary services like Multi-Threaded HTTP Server for Zimbra.
• Asset and patch process: Establish a regular patch review cycle for all third-party components, including Zimbra add-ons.

7. Risks, Side Effects, and Roll Back

Blocking access may disrupt legitimate users if the server is required. Disabling it could affect functionality.

• Risk or side effect 2: Disabling Multi-Threaded HTTP Server for Zimbra could affect specific features. Mitigation: Test thoroughly in a non-production environment first.
• Roll back: Step 1: Re-enable the server within the Zimbra configuration. Step 2: Remove any firewall rules blocking access to port 8080. Step 3: Restart the Zimbra service.

8. References and Resources

• Vendor advisory or bulletin: No specific vendor advisory was provided in the context.
• NVD or CVE entry: No CVE number was provided in the context.
• Product or platform documentation relevant to the fix: https://www.exploit-db.com/exploits/12304/