Top 10 SSL/TLS Misconfigurations, Risks and It’s Solutions

SSL/TLS encryption protects online communication, but minor configuration errors can create serious security risks. Misconfigured SSL/TLS settings can expose sensitive data, leaving websites vulnerable to cyberattacks.

71% of organization’s reported SSL/TLS-related attacks last year. According to OWASP, a staggering 90% of applications tested in 2021 had some form of misconfiguration.

These errors are outdated protocols and weak cipher suites. That can make weak encryption, and attackers could exploit these security flaws. Understanding and addressing SSL/TLS misconfigurations is important to maintaining a secure and strong online presence.

These misconfigurations have been exploited by hackers for a long time. They intercept data traffic, perform man-in-the-middle attacks, or downgrade encryption protocols. Some of the common mistakes are using expired or self-signed certific

ates, enabling weak ciphers, and failing to enforce HTTPS properly. These could lead to user data breaches, trust damage, and regulatory penalties. In this blog, we are going to see the top 10 SSL/TLS misconfigurations.

What is SSL and TLS?

Secure Sockets Layer (SSL) and Transport Layer Security (TLS), are cryptographic protocols designed to secure communication over the internet. When a user visits a web site, the server sends the data to the user’s browser, and all this data passes through different network devices across the internet.

To protect this data so only the user to whom it belongs can get this data, the SSL and TLS protocol is used, which encrypts data transferred between clients (such as web browsers) and servers. It also gives data integrity, showing that no 3^rd person can do any small changes to this data in middleware.

Netscape introduced the Secure Sockets Layer (SSL) protocol in 1994 to address the growing need for secure data transmission over the internet, particularly for web browsers and other TCP-based protocols.

However, SSL 1.0 was never officially released due to significant security vulnerabilities. The first public version, SSL 2.0, was launched in 1995, followed by the final iteration, SSL 3.0, which was released in November 1996.

As SSL became outdated due to security vulnerabilities, Transport Layer Security (TLS) was introduced as its successor. TLS has four versions, TLS 1.0, TLS 1.1, TLS 1.2 and TLS 1.3, each version has better than SSL.

It has many advantages over SSL, such as it supports strong and modern cryptography, Improved Handshake Process, Better Authentication, Protection Against Known Attacks and Session Resumption. Nowadays TLS 1.2 and TLS 1.3 are widely used over the internet.

Advantages of TLS Over SSL

Stronger Encryption – TLS supports modern cryptographic algorithms, such as AES-GCM and ChaCha20, which provide better security than older SSL ciphers.

Improved Handshake Process – TLS reduces latency by optimizing the handshake process, making secure connections faster.

Better Authentication – Supports more robust authentication mechanisms, such as certificate pinning and Perfect Forward Secrecy (PFS).

Protection Against Known Attacks – Fixes vulnerabilities found in SSL, such as POODLE, BEAST, and DROWN.

Session Resumption – TLS improves session resumption techniques, reducing overhead and improving performance for repeated connections.

About SSL/TLS Protocols

It works on a handshake process where the client and server agree on the encryption algorithms and keys to be used for the session.

These protocols establish a secure connection by utilizing a combination of encryption algorithms, key exchange methods, and digital certificates. Encryption algorithms, such as AES, ensure that data is encrypted and can only be decrypted by the intended recipient.

Key exchange mechanisms, like Diffie-Hellman, facilitate the secure transfer of cryptographic keys between the client and server. Additionally, digital certificates, issued by trusted Certificate Authorities (CAs), authenticate the identities of both parties, further enhancing the security of the communication.

The Top 10 SSL/TLS Misconfigurations & Solutions

Here are the top 10 SSL/TLS misconfigurations, their risks, and how to fix them.

Using Weak or Deprecated Cipher Suites

It violates many top security standards, such as NIST, the problem here is that older algorithms use small key sizes, which can be easily broken with today’s computation power. It also lacks Perfect Forward Secrecy (PFS), meaning that if a private key is compromised, all past communications using that key can be decrypted.

Using weak or deprecated cipher suites is a major security risk. These outdated cryptographic algorithms can be exploited by attackers to decrypt sensitive data, perform man-in-the-middle (MITM) attacks, or compromise the confidentiality and integrity of communications.

The encryption algorithms like RC4 or hash functions based on MD5 can leave your site vulnerable to attacks such as BEAST (Browser Exploit Against SSL/TLS), POODLE (Padding Oracle On Downgraded Legacy Encryption), Logjam (Weak Diffie-Hellman Key Exchange), and SWEET32 (Birthday Attack on 64-bit Block Ciphers).

Flaws in cipher block chaining (CBC) within SSL/TLS protocols can result in ciphertext collisions, potentially enabling attackers to decrypt and recover sensitive plaintext data.

How to Test?

Here are some methods which check if your site is affected by this misconfiguration or not.

Method 1: You can use SSL online tools to check your site.

Method 2: You can use command line tools such as Nmap and OpenSSL.

For OpenSSL run this command:

openssl s_client -connect example.com:443 -cipher LOW

For Nmap use:

nmap --script ssl-enum-ciphers -p 443 example.com

How to Fix it?

Update your server configuration to implement secure, modern cipher suites such as AES-GCM with SHA-256, while eliminating outdated and deprecated options.

Follow these steps to fix in Apache and CentOS/RHEL.

Step 1: Open the configuration file
           For Apache:  “ sudo nano /etc/apache2/apache2.conf ”

          For CentOS/RHEL: “ sudo nano /etc/httpd/conf/httpd.conf  ”

Step 2: Add or update the following SSL configuration.

SSLProtocol -SSLv2 -SSLv3 -TLSv1 -TLSv1.1 +TLSv1.2 +TLSv1.3

SSLCipherSuite HIGH:!aNULL:!MD5:!RC4:!3DES:!SHA1

SSLHonorCipherOrder on

Step 3: Save ( Ctrl + X, then Y, then Enter ) the configuration file and restart the server for Apache “ sudo systemctl restart apache2 ” and for CentOS/RHEL “ sudo systemctl restart httpd ”.

Allowing SSL/TLS Version Downgrade

The old SSL/TLS cryptographic algorithms are vulnerable to this attack, which allows the attackers to downgrade the version to weak encryption protocols such as “SSL 3.0“ and “TLS 1.0/1.1“.

It violates compliance standards and makes your system vulnerable to man-in-the-middle (MITM) attacks such as POODLE Attack, Downgrade Attacks (e.g., TLS_Downgrade_SCSV Bypass) and Forced Fallback Attacks (e.g., BEAST, FREAK, Logjam).

How to Test?

You can check if your site has this misconfiguration or not by the following steps.

Method 1: Use the Nmap tool in your system and run the following nmap-script.

“ nmap --script ssl-enum-ciphers -p 443 example.com ”

Method 2: You can use an online tool, such as https://www.ssllabs.com/ssltest/ just enter your website domain name and submit. It will check and give you the report.

How to Fix it?

Here We will show you with the example of Nginx server because in the previous misconfiguration We used Apache. Steps for fixing it on different web servers are similar. We are using a different example so you will get familiar with different servers. Just follow the steps:

Step 1: Open Nginx server configuration file. “ sudo nano /etc/nginx/nginx.conf ”

Step 2: Add the following and update it

ssl_protocols TLSv1.2 TLSv1.3;
ssl_prefer_server_ciphers on;

Step 3: Save the file ( Ctrl + X, then Y, then Enter).

Step 4: Restart the Nginx server, just run the following command:

sudo systemctl restart nginx

Self-Signed or Expired Certificates

Self-signed or expired SSL/TLS certificates create trust issues. It triggers browser warnings and makes users vulnerable to Man-in-the-Middle (MITM) attacks.

Also Read: How to Check TLS/SSL Certificate Expiration Date?

When browsers or applications do not trust a certificate, they warn users, who may ignore the warning, allowing attackers to intercept or manipulate data.

The problem with Self-signed or expired SSL/TLS certificates is that Attackers can spoof it and trick users into connecting to a fake website. Organisations use it internally, which may expose APIs, applications, or internal services to security risks.

How to Detect and Fix it?

To prevent it, we can use the following solution.

1. Don’t use self-signed certificates, instead we can Buy SSL Certificate from the Certificate Authorities (CAs) such as DigiCert. Sectigo or Certera.
2. Use a Certificate management tool, which can automatically renew the expired certificate, monitor the certificate expiration to prevent downtime or security risks.

Misconfigured Certificate Chains

A certificate chain misconfiguration happens when a server fails to include the necessary intermediate certificates that connect the SSL certificate to a trusted root certificate. This can result in validation failures, disrupted HTTPS connections, and potential security vulnerabilities.

Certificate chain is a sequence of certificates that verifies the validity of an SSL/TLS certificate issued to a website or service. It ensures trust by linking your server certificate to a trusted root Certificate Authority (CA) through intermediate certificates.

How to Test?

Method 1: Use this online tool SSL Labs to check for misconfiguration of the certificate chain.

Method 2: Alternatively, use OpenSSL command line tool and run the following command.

openssl s_client -connect example.com:443 -showcerts

How to Fix it?

How to fix this error in Windows IIS server. Just follow these steps.

Step 1: Open IIS Manager → Select your site → Click Bindings.

Step 2: Select HTTPS, then click Edit → Browse for the full certificate (PFX format).

Step 3: Ensure you install the entire certificate chain, not just the server certificate.

Step 4: Restart IIS, run this PowerShell command “iisreset”

Failing to Enable Perfect Forward Secrecy (PFS)

Not enabling Perfect Forward Secrecy (PFS) means a server or system lacks a crucial security measure that generates unique session keys for each communication session.

Without PFS, if the server’s long-term private key is ever compromised, attackers could decrypt previously recorded encrypted communications, exposing sensitive data.

Use key exchange algorithms that support PFS, such as ECDHE (Elliptic Curve Diffie-Hellman Ephemeral) and Diffie-Hellman Ephemeral (DHE). They have unique encryption keys for each session.

How to Test?

To Check If Your Server Uses PFS, Run this OpenSSL command. If it fails, your server doesn’t support PFS.

openssl s_client -connect example.com:443 -cipher ECDHE-RSA-AES128-GCM-SHA256

How to Fix it?

Enable PFX in the Nginx server, follow these steps.

Step 1: Open this Apache configuration file.

sudo nano /etc/apache2/sites-available/default-ssl.conf

Step 2: Add this to the configuration file.

SSLCipherSuite HIGH:!aNULL:!MD5:!RC4:!3DES
SSLHonorCipherOrder on
SSLProtocol all -SSLv2 -SSLv3

Step 3: Restart the Apache server.

sudo systemctl restart apache2

Not Disabling Insecure Protocols

Failing to disable insecure protocols means that a system administrator or network operator continues to support outdated and vulnerable encryption protocols, such as SSLv3 or older TLS versions. This oversight increases the system’s exposure to potential security threats and exploits.

How to Test?

Run the following OpenSSL command. If the connection succeeds, SSL 3.0 is still enabled and should be disabled.

openssl s_client -connect example.com:443 -ssl3

How to Fix?

To fix this misconfiguration in the Apache server, follow these steps.

Step 1: Edit this Apache configuration file.

 sudo nano /etc/apache2/sites-available/default-ssl.conf

Step 2: Add this to the configuration file.

SSLProtocol all -SSLv2 -SSLv3 -TLSv1 -TLSv1.1

Step 3: Restart the server with sudo systemctl restart apache2

Lack of OCSP Stapling

This does mean that a web server doesn’t use the Online Certificate Status Protocol (OCSP) stapling feature. Therefore, there is no direct communication of the revocation status of the certificate during the TLS handshake, and the client must ask the CA itself. It also may lead to slower connection times or even privacy risks.

How to Test?

Run the following OpenSSL command (“ openssl s_client -connect example.com:443 -status ”), if the response includes “ OCSP Response: No response sent ”, then OCSP Stapling is NOT enabled.

How to Fix?

To fix this in the Apache server, follow these steps.

Step 1: Open this configuration file.
sudo nano /etc/apache2/sites-available/default-ssl.conf

Step 2: Add and update this to the configuration file.

SSLUseStapling on
SSLStaplingCache shmcb:/tmp/stapling_cache(128000)
SSLStaplingResponderTimeout 5

Step 3: Restart the server. (“ sudo systemctl restart apache2 ”)

Misconfigured Server Name Indication (SNI)

Misconfigured Server Name Indication (SNI) occurs when a web server is not correctly configured to handle the SNI extension in the TLS protocol. This can result in improper certificate selection, security vulnerabilities, or difficulties in hosting multiple websites on the same IP address.

Essentially, the server fails to correctly identify the domain a client is requesting during the TLS handshake, leading to potential connection issues.

How to Test?

Run the following OpenSSL command (“ openssl s_client -connect example.com:443 -servername example.com ”). If the wrong certificate is returned, your SNI setup is misconfigured.

How to Fix it?

To fix it on Apache follow these steps.

Step 1: Check Apache supports SNI by running this command.

apachectl -M | grep ssl

Step 2: If ssl_module is not listed, enable it by this.

sudo a2enmod ssl
sudo systemctl restart apache2

Step 3: Correct VirtualHost Configuration, Make sure each domain has its own VirtualHost entry with the correct SSL certificate.

<VirtualHost *:443>
ServerName example.com
DocumentRoot /var/www/example
 SSLEngine on
 SSLCertificateFile /etc/ssl/certs/example.com.crt
 SSLCertificateKeyFile /etc/ssl/private/example.com.key
</VirtualHost>
<VirtualHost *:443>
    ServerName anotherdomain.com
    DocumentRoot /var/www/anotherdomain
    SSLEngine on
    SSLCertificateFile /etc/ssl/certs/anotherdomain.com.crt
    SSLCertificateKeyFile /etc/ssl/private/anotherdomain.com.key
</VirtualHost>

Incorrect DNS Configuration for SSL/TLS

When the domain name in the DNS server does not correctly point to the server hosting the SSL certificate. This can cause HTTPS access errors, as the browser fails to verify the certificate with the correct domain.

How to Test?

Use the following command line tool to check DNS resolution. Check if it resolves to the correct IP address where your SSL certificate is installed.

dig example.com

How to Fix it?

Follow the below steps and correct the DNS configuration.

Step 1: Check that your DNS record, such as A record (IPv4) and AAAA record (IPv6), point to the correct server. If not the correct it.

Step 2: Fix the subdomain DNS record.

Unsafe SSL/TLS Renegotiation Settings

The unsafe SSL/TLS renegotiation setting means that a server allows clients to retry an SSL/TLS connection without sufficient security controls.

It can expose your server to security risks, such as the “Triple Handshake” attack, which allows attackers to intercept secure connections.

How to Test?

Run the following OpenSSL command.

openssl s_client -connect example.com:443 -reconnect

How to Fix?

Follow this step to fix it in the Apache server.

Step 1: Edit your Apache SSL configuration file.

sudo nano /etc/apache2/mods-available/ssl.conf

Step 2: Add this to the configuration file.

SSLInsecureRenegotiation off

STEP 3: Restart the server.

sudo systemctl restart apache2

Conclusion

Securing your SSL/TLS configurations is essential for protecting sensitive data and preventing cyber threats. Misconfigurations can expose your website to attacks like man-in-the-middle, protocol downgrade, and weak encryption exploits.

By implementing SSL best practices, regularly monitoring certificates, and ensuring compliance with modern security standards, you can maintain a strong defense against potential vulnerabilities.

Need help managing SSL/TLS certificates or securing your digital environment? Contact us today for SSL/TLS certificate solutions to keep your website safe and compliant.

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