How to remediate – SSL/TLS Certificate Information

1. Introduction

The SSL/TLS Certificate Information vulnerability concerns details about the X.509 certificate used on HTTPS connections. This information can be used to identify potential misconfigurations or weaknesses in a server’s security setup. Systems using HTTPS, such as web servers and email services, are typically affected. A weak certificate configuration could allow attackers to intercept encrypted traffic, potentially impacting confidentiality, integrity, and availability.

2. Technical Explanation

This issue isn’t a direct exploit but highlights the importance of proper certificate management. An attacker can gather information about certificates to identify outdated or improperly configured servers. This could lead to man-in-the-middle attacks if weak ciphers are enabled, or reveal internal server details. There is no specific CVE associated with simply displaying certificate information; however, misconfigured certificates often fall under vulnerabilities like weak cipher suites (CVEs vary). An attacker might use tools like `openssl s_client` to connect to an HTTPS server and examine the returned certificate chain.

• Root cause: The plugin displays certificate details without actively checking for weaknesses.
• Exploit mechanism: An attacker uses publicly available tools to gather certificate information, then identifies servers with weak configurations or expired certificates.
• Scope: Any system using HTTPS is potentially affected, including Apache, Nginx, IIS web servers and email servers.

3. Detection and Assessment

You can confirm whether a system displays certificate information by connecting to the HTTPS endpoint and examining the output. A thorough method involves scanning for weak certificates.

• Quick checks: Use a web browser to connect to the HTTPS site, view the certificate details (usually in Site Information or Connection settings), and check the expiry date.
• Scanning: Nessus plugin ID 69478 can identify SSL/TLS certificate issues. OpenVAS also has relevant scanners. These are examples only.
• Logs and evidence: Web server logs may show details of TLS handshakes, including certificate information. Event IDs will vary by web server software.

openssl s_client -connect example.com:443

4. Solution / Remediation Steps

The solution involves ensuring certificates are valid and properly configured.

4.1 Preparation

• Ensure you have access to a Certificate Authority (CA) or can generate self-signed certificates. A roll back plan involves restoring the original web server configuration.
• A change window may be needed for production systems, requiring approval from IT management.

4.2 Implementation

1. Step 1: Verify your SSL/TLS certificate is valid and not expired.
2. Step 2: Ensure the certificate chain is complete and correctly configured on your web server.
3. Step 3: Configure your web server to use strong cipher suites.
4. Step 4: Restart the web service to apply changes.

4.3 Config or Code Example

Before

# Example Apache configuration with weak ciphers
SSLCipherSuite ALL

After

# Example Apache configuration with strong ciphers
SSLCipherSuite ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this issue.

• Practice 1: Patch cadence – Regularly update your web server software and SSL/TLS libraries to address known vulnerabilities.
• Practice 2: Secure defaults – Configure your web server with strong cipher suites and protocols by default.

4.5 Automation (Optional)

If suitable, provide a small script or infrastructure code that applies the fix at scale. Only include if safe and directly relevant.

# Example Bash script to check certificate expiry (requires openssl)
#!/bin/bash
domain="example.com"
expiry=$(openssl s_client -connect "$domain":443 2>/dev/null | openssl x509 -noout -dates)
echo "Certificate for $domain expires on: $expiry"

5. Verification / Validation

Confirm the fix by verifying the certificate details and re-running detection scans.

• Post-fix check: Use `openssl s_client -connect example.com:443` and verify the expiry date is in the future.
• Re-test: Re-run Nessus plugin ID 69478 or OpenVAS scans to confirm no vulnerabilities are reported.
• Smoke test: Access your website via HTTPS to ensure it loads correctly. Test key functionality like login and form submission.
• Monitoring: Monitor web server logs for TLS handshake errors, which could indicate certificate issues.

openssl s_client -connect example.com:443 | grep "expire date"

6. Preventive Measures and Monitoring

Update security baselines and add checks to your CI/CD pipeline.

• Baselines: Update your security baseline or policy to require valid SSL/TLS certificates with strong cipher suites (for example, CIS control 1.2).
• Asset and patch process: Implement a regular review cycle of all SSL/TLS certificates across your infrastructure.

7. Risks, Side Effects, and Roll Back

Incorrectly configuring the web server can cause service outages.

• Risk or side effect 2: Expired certificate will result in website downtime and browser warnings. Mitigation: Monitor certificate expiry dates closely.
• Roll back: Restore the original web server configuration file from your backup. Restart the web service.

8. References and Resources

Link only to sources that match this exact vulnerability.

• Vendor advisory or bulletin: [https://httpd.apache.org/security/](https://httpd.apache.org/security/)
• NVD or CVE entry: Search NVD for relevant SSL/TLS vulnerabilities (e.g., weak cipher suites).
• Product or platform documentation relevant to the fix: [https://docs.nginx.com/en/latest/http/configuring_https_certificates.html](https://docs.nginx.com/en/latest/http/configuring_https_certificates.html)