The POODLE (Padding Oracle On Downgraded Legacy Encryption) vulnerability fundamentally exploits SSL 3.0's weak cipher block chaining, allowing man-in-the-middle attackers to decrypt secure connections. While disabling SSLv3 appears straightforward, the reality involves nuanced compatibility considerations.

When a client attempts HTTPS connection:

ClientHello (offers TLS 1.2, TLS 1.1, SSLv3)
↓
Server responds with highest mutually supported version
↓
If only SSLv3 is common, vulnerable connection established

For Apache 2.4+, complete SSLv3 elimination:

SSLProtocol all -SSLv3 -SSLv2 -TLSv1 -TLSv1.1
SSLHonorCipherOrder on
SSLCipherSuite "EECDH+ECDSA+AESGCM EECDH+aRSA+AESGCM EECDH+ECDSA+SHA384 EECDH+ECDSA+SHA256"

Modern browsers handle TLS fallback gracefully:

• Chrome 39+ (2014) disabled SSLv3 by default
• Firefox 34+ implements TLS_FALLBACK_SCSV
• IE11 uses TLS 1.2 as default

Disabling SSLv3 affects approximately:

Beyond protocol disabling, enforce perfect forward secrecy:

# Nginx configuration
ssl_prefer_server_ciphers on;
ssl_dhparam /etc/ssl/certs/dhparam.pem;
ssl_ciphers 'ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305';

Post-implementation checks using OpenSSL:

openssl s_client -connect example.com:443 -ssl3 # Should fail
openssl s_client -connect example.com:443 -tls1_2 # Should succeed

When absolute SSLv3 removal isn't feasible:

1. Implement TLS_FALLBACK_SCSV at load balancers
2. Use HSTS headers with preload option
3. Deploy network-layer SSL inspection

The Padding Oracle On Downgraded Legacy Encryption (POODLE) attack exploits SSL 3.0's vulnerability to cipher block chaining (CBC) mode padding checks. While TLS implementations have protection against this attack vector, SSLv3 remains vulnerable due to its design limitations from 1996.

For Apache servers running on Linux, here's the proper SSL protocol configuration in httpd.conf or ssl.conf:

<VirtualHost *:443>
    SSLEngine on
    SSLProtocol all -SSLv2 -SSLv3
    SSLCipherSuite HIGH:!aNULL:!MD5:!RC4:!3DES
    SSLHonorCipherOrder on
    # Other SSL configurations...
</VirtualHost>

When disabling SSLv3, you might encounter these common scenarios:

• Android 2.x-4.0 devices (native browser) will fail to connect
• IE6 on Windows XP without updates will fail
• Java 6 clients may experience connection issues

For enterprises needing legacy support, consider these approaches:

# Nginx configuration allowing fallback for known legacy clients
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_ciphers 'ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305...';

# Conditional SSLv3 enablement based on User-Agent
map $http_user_agent $allow_sslv3 {
    default 0;
    "~*MSIE 6" 1;
    "~*Android 2" 1;
}

server {
    ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
    ssl_protocols SSLv3 if $allow_sslv3;
}

Use OpenSSL to test your configuration:

openssl s_client -connect yourdomain.com:443 -ssl3
# Should return: "error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure"

# Comprehensive test using testssl.sh
./testssl.sh -p -S yourdomain.com

If complete SSLv3 disablement isn't feasible:

1. Implement TLS_FALLBACK_SCSV to prevent protocol downgrade attacks
2. Use application-layer protections like HSTS with includeSubDomains
3. Consider deploying separate legacy endpoints with strict access controls