How To Fix 526 Invalid SSL Certificate Error

Fix 526 Invalid SSL Certificate Error

In today’s digital landscape, securing sensitive information and maintaining user trust is paramount for any website owner. SSL certificates play a crucial role in encrypting data and providing a secure connection between the user’s browser and the web server. However, encountering errors like the 526 Invalid SSL Certificate can disrupt this crucial security layer and lead to potential vulnerabilities.

In this comprehensive guide, we will delve into the 526 Invalid SSL Certificate error, understand its causes, and explore step-by-step instructions to fix it using the command line. Whether you’re a seasoned system administrator or a website owner, our SEO-optimized guide will equip you with the knowledge and confidence to address this issue swiftly and effectively.

Causes of the 526 Invalid SSL Certificate Error

Before we dive into the solutions, let’s explore the root causes of the 526 Invalid SSL Certificate error to gain a better understanding of the problem:

A. Expired SSL Certificate: An SSL certificate comes with a validity period, typically ranging from a few months to a couple of years. If the certificate has expired, the server will not establish a secure connection, triggering the 526 error.

B. Misconfigured SSL Certificate: Incorrect configuration of the SSL certificate can lead to handshake failures, causing the 526 error. This misconfiguration may involve incorrect intermediate certificates, key file issues, or improper settings.

C. SSL Certificate Not Issued by a Trusted CA: Browsers trust SSL certificates signed by recognized Certificate Authorities (CAs). If your certificate is self-signed or issued by an untrusted CA, users will encounter the 526 error.

D. Mismatched Common Name (CN) in SSL Certificate: The Common Name (CN) in the SSL certificate should match the domain name of the website. A mismatch between the two will result in the 526 error.

E. Server Configuration Issues: Inadequate server configurations, such as outdated protocols or cipher suites, can also contribute to the 526 error. Keeping server configurations up-to-date is crucial for maintaining SSL compatibility.

Preparing Your Environment for the Fix

Before delving into the troubleshooting steps, ensure you have the necessary tools and access to the server’s command line interface. Additionally, gather the following information:

A. Accessing the Command Line Interface (CLI): To access the command line, log in to your server using Secure Shell (SSH) or other remote access methods.

B. Verifying Server Connectivity: Confirm that your server has an active internet connection to perform necessary tasks.

C. Gathering Necessary Information: Note down the server’s IP address, domain name, and SSL certificate details (if available).

Step-by-Step Guide to Fixing the 526 Error with Command Line

Now that we have a clear understanding of the error’s causes and prepared our environment, let’s proceed with the step-by-step troubleshooting process.

A. Checking SSL Certificate Expiry Date:

  • Open your terminal or command prompt.
  • Use OpenSSL to check the expiry date of your SSL certificate using the following command:

openssl x509 -enddate -noout -in /path/to/your/certificate.pem

The command will display the certificate’s expiration date, allowing you to determine if it’s the cause of the 526 error.

  • If the certificate has expired or will expire soon, consider obtaining a new certificate from your CA and proceed to the next step.

B. Verifying SSL Certificate Configuration:

  • Run the following command to retrieve the details of your SSL certificate:
openssl x509 -text -noout -in /path/to/your/certificate.pem
  • Verify the certificate details, including the common name (CN), issuer, and other relevant information. Ensure that the CN matches your domain name.

  • If you find any discrepancies or misconfigurations, correct them and proceed to the next step.

C. Updating/Replacing the SSL Certificate:

  1. Obtain a new SSL certificate from a trusted CA. Many CAs provide detailed guides on how to generate and install SSL certificates.

  2. Follow your CA’s instructions to install the new certificate on your server.
  3. Restart your web server to apply the changes.

D. Ensuring Certificate Authority Trust:

  1. If you have a self-signed certificate or one issued by an untrusted CA, consider switching to a certificate from a recognized and trusted CA.

  2. Add the root and intermediate certificates from the CA to your server’s trusted certificate store.

  3. Once the trusted certificates are installed, restart your web server to implement the changes.

E. Matching Common Name (CN) in SSL Certificate:

  1. Run the following command to check the CN in your SSL certificate:
openssl x509 -noout -subject -in /path/to/your/certificate.pem
  1. Ensure that the CN displayed matches your domain name.
  2. If the CN does not match, obtain a new certificate with the correct CN or reconfigure the existing one accordingly.

F. Fixing Server Configuration Issues:

  1. Check your server’s SSL configuration to ensure it supports modern encryption standards and secure protocols.
  2. Update your web server’s configuration file (e.g., Apache or Nginx) to enable the appropriate SSL settings.
  3. Restart the webserver to apply the changes.

Common Challenges and How to Overcome Them

While troubleshooting the 526 error, you may encounter some common challenges. Let’s explore how to overcome them:

A. Permission Issues while Updating SSL Certificate:

  1. Ensure that you have sufficient permissions to modify SSL certificate files and directories.
  2. Use the ‘chown‘ and ‘chmod‘ commands to grant the necessary permissions:
chown -R your_user:your_group /path/to/certificate_directory
chmod -R 600 /path/to/certificate_directory
  1. Retry the certificate update process.

B. Troubleshooting Certificate Authority Verification Failures:

  1. If you face CA verification issues, check your server’s time and date settings. Correct any discrepancies to ensure proper certificate validation.

  2. Verify that your server’s CA bundle is up-to-date and contains the required root and intermediate certificates.
  3. Consider using the ‘update-ca-certificates’ command on Linux-based systems to update the CA bundle.

C. Dealing with Certificate Chain Issues:

  • If the SSL certificate chain is incomplete, download and install the missing intermediate certificates from your CA’s website.
  • Concatenate the intermediate certificates to your SSL certificate file:

cat intermediate1.crt intermediate2.crt >> certificate.pem
  • Verify the certificate chain with the ‘OpenSSL verify’ command:
openssl verify -CAfile /path/to/ca_bundle.crt /path/to/your/certificate.pem

D. Identifying and Fixing Common Name Mismatch:

  1. Double-check the common name (CN) specified during the SSL certificate generation process.

  2. Update the certificate with the correct CN or reissue it with the right information.
  3. Ensure that your web server’s virtual host configuration corresponds to the correct CN.

Testing Your SSL Certificate after the Fix

After applying the necessary fixes, it’s essential to test your SSL certificate to ensure a successful resolution. Several online SSL checker tools can assist you in this process. These tools validate your SSL installation and provide detailed reports on its configuration and security.

Additionally, you can use the following command to test your SSL certificate from the command line:

openssl s_client -connect your_domain:443

The output will display SSL certificate information, including the certificate chain and validity.

Tips for SSL Certificate Maintenance and Best Practices

To ensure a robust and secure SSL environment, consider the following maintenance tips and best practices:

  • Regularly Monitor SSL Certificate Expiry: Keep track of your SSL certificate’s expiration date and set up timely reminders for renewal.
  • Keep SSL Certificates Updated: Regularly update your SSL certificates to stay ahead of potential vulnerabilities.
  • Backup SSL Certificates and Private Keys: Maintain backups of your SSL certificates and private keys in secure locations.
  • Stay Informed about SSL Industry Updates: Stay informed about the latest SSL industry trends, security updates, and best practices.
  • Enable Automatic Certificate Renewal: Consider setting up automatic certificate renewal to avoid unexpected expirations.


Securing your website with a valid SSL certificate is crucial for protecting user data and maintaining trust. The 526 Invalid SSL Certificate error can be disruptive, but armed with the knowledge provided in this guide, you can troubleshoot and resolve the issue using the command line. By following the step-by-step instructions and implementing best practices, you ensure a safe and secure online environment for your visitors.

Remember, SSL certificate management is an ongoing process, and regular maintenance is essential to keep your website secure and reliable. Stay proactive, stay informed, and stay committed to providing a secure browsing experience for your users.


r00t is a seasoned Linux system administrator with a wealth of experience in the field. Known for his contributions to, r00t has authored numerous tutorials and guides, helping users navigate the complexities of Linux systems. His expertise spans across various Linux distributions, including Ubuntu, CentOS, and Debian. r00t's work is characterized by his ability to simplify complex concepts, making Linux more accessible to users of all skill levels. His dedication to the Linux community and his commitment to sharing knowledge makes him a respected figure in the field.
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