TLS/SSL Misconfigurations

TLS security depends on both the protocol version and the cipher suites negotiated. Legacy configurations expose HTTPS traffic to practical attacks.

Deprecated protocol versions:

• SSL 2.0 / SSL 3.0: Broken, vulnerable to POODLE, BEAST. Must be disabled.
• TLS 1.0 / TLS 1.1: Deprecated by RFC 8996. Vulnerable to known attacks. Disable.
• TLS 1.2: Acceptable with strong cipher suites.
• TLS 1.3: Recommended. Removes weak cipher options entirely.

Weak cipher suites to disable:

• RC4 - broken stream cipher (NOMORE attack)
• DES / 3DES - short keys, SWEET32 attack
• NULL cipher - no encryption
• EXPORT ciphers - deliberately weakened
• Anonymous DH - no server authentication

Check your server with:

nmap --script ssl-enum-ciphers -p 443 example.com
openssl s_client -connect example.com:443 -tls1
# Or use Qualys SSL Labs online test

Configure your web server to require TLS 1.2+ and only allow strong cipher suites.

Nginx TLS hardening:

server {
  listen 443 ssl;
  
  # TLS versions
  ssl_protocols TLSv1.2 TLSv1.3;  # Disable SSLv2, SSLv3, TLS 1.0, TLS 1.1
  
  # Strong cipher suites
  ssl_ciphers "ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:
    ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:
    TLS_AES_128_GCM_SHA256:TLS_AES_256_GCM_SHA384";
  ssl_prefer_server_ciphers off;  # Let client choose for TLS 1.3
  
  # Perfect Forward Secrecy
  ssl_session_cache shared:SSL:10m;
  ssl_session_timeout 1d;
  ssl_session_tickets off;  # Disable for PFS
  
  # HSTS
  add_header Strict-Transport-Security "max-age=63072000" always;
}

Defense checklist:

• Enable only TLS 1.2 and TLS 1.3
• Disable all export, NULL, anonymous, RC4, DES ciphers
• Prefer ECDHE key exchange for forward secrecy
• Use certificates from a trusted CA with 2048+ bit RSA or 256+ bit ECDSA keys
• Regularly test with Qualys SSL Labs or testssl.sh