If you maintain a web server, the safest short-term response is to disable SSLv3 support (or disable CBC-mode ciphers in coordination with SSLv3). The protocol is more than fifteen years old and the current versions of all major web browsers have supported TLS 1.0 since 2006. It is also important to remember that many protocols other than HTTPS utilize TLS for transport security, including POP3, IMAP, SMTP, XMPP, FTP, and NNTP.

We've included instructions on how to disable SSLv3 support for the following products below.

What clients do not support TLS?

The largest userbase that will be affected by a lack of TLS support are Internet Explorer clients using IE6 or below. It is estimated that 3.8% of all clients are still running IE6, but IE6 only represents 0.1% of US browsers. Opera began supporting TLS in version 5, and TLS support was present in Firefox 2 (and possibly earlier versions). All versions of Google Chrome support TLS. A more long-term solution is to use TLS Signaling Cipher Suite Value (SCSV).

How can I test my server?

If you have a public web server, you can test it using the Qualys SSL Server Test. You can also test private web servers and other TLS endpoints using OpenSSL by running openssl s_client -ssl -connect fqdn:port. If your server has SSLv3 disabled, you will receive a handshake error, otherwise, you'll receive the same output as when you run openssl s_client -connect fqdn:port.

nginx

Modify the ssl_protocols directive to only use TLSv1, TLSv1.1, and TLSv1.2. If you do not have a ssl_protocols directive, add it to the top of your configuration file.

ssl_protocols TLSv1 TLSv1.1 TLSv1.2;

Apache

The SSL configuration file changed slightly in httpd version 2.2.23. For httpd version 2.2.23 and newer, specify all protocols except SSLv2 and SSLv3.

SSLProtocol ALL -SSLv2 -SSLv3

For httpd version 2.2.22 and older, only specify TLSv1. This is treated as a wildcard for all TLS versions.

SSLProtocol TLSv1

For Apache + mod_nss, edit /etc/httpd/conf.d/nss.conf to allow only TLS 1.0+.

NSSProtocol TLSv1.0,TLSv1.1

Microsoft IIS

Please see the write-up at digicert for how to disable SSLv3.

Postfix SMTP

Thanks to gertvdijk on AskUbuntu.

Modify the smtpd_tls_mandatory_protocols configuration line.

smtpd_tls_mandatory_protocols=!SSLv2,!SSLv3

Sendmail

Thanks to gertvdijk on AskUbuntu.

Modify the LOCAL_CONFIG section of the sendmail.mc file.

CipherList=HIGH

ServerSSLOptions=+SSL_OP_NO_SSLv2 +SSL_OP_NO_SSLv3 +SSL_OP_CIPHER_SERVER_PREFERENCE

ClientSSLOptions=+SSL_OP_NO_SSLv2 +SSL_OP_NO_SSLv3

Dovecot

Thanks to gertvdijk on AskUbuntu.

For Dovecot 2.1+, edit /etc/dovecot/local.conf to add the below lines and then restart Dovecot.

ssl_protocols = !SSLv2 !SSLv3

For Dovecot 2, edit /etc/dovecot/conf.d/10-ssl.conf to add the below lines and then restart Dovecot.

ssl_cipher_list = ALL:!LOW:!SSLv2:!SSLv3:!EXP:!aNULL

HAProxy Server

Thanks to gertvdijk on AskUbuntu.

Edit the bind line in your /etc/haproxy.cfb file.

bind :443 ssl crt  ciphers  no-sslv3

389 Directory Server

Thanks to Loris Santamaria.

Modify cn=encryption,cn=configA and restart the server.

ldapmodify -x -D "cn=Directory Manager" -W <<EOF

dn: cn=encryption,cn=config

changetype: modify

replace: nsSSL3

nsSSL3: off

Courier-imap

Thanks to gertvdijk on AskUbuntu.

For Ubuntu 12.04, edit /etc/courier/imapd-ssl.

IMAPDSSLSTART=NO

IMAPDSTARTTLS=YES

IMAP_TLS_REQUIRED=1

TLS_PROTOCOL=TLS1

TLS_STARTTLS_PROTOCOL=TLS1

Lighttpd

Thanks to gertvdijk on AskUbuntu.

For Lighttpd 1.4.28+, edit /etc/lighttpd/lighttpd.conf

ssl.use-sslv2 = "disable"

ssl.use-sslv3 = "disable"

On versions of Lighttpd older than < 1.4.28, there is no elegant solution to disableing SSLv4, but you can disable SSLv3 by specifically disabling SSLv3 cipher suites (in ssl.cipher-list). Allowable suites are: 

ECDHE-ECDSA-CAMELLIA256-SHA384 ECDHE-ECDSA-AES256-GCM-SHA384
ECDHE-ECDSA-AES256-SHA384 ECDHE-ECDSA-AES256-SHA
ECDHE-RSA-CAMELLIA256-SHA384 ECDHE-RSA-AES256-GCM-SHA384
ECDHE-RSA-AES256-SHA384 ECDHE-RSA-AES256-SHA DHE-DSS-CAMELLIA256-SHA
DHE-DSS-AES256-GCM-SHA384 DHE-DSS-AES256-SHA256 DHE-DSS-AES256-SHA
DHE-RSA-CAMELLIA256-SHA DHE-RSA-AES256-GCM-SHA384 DHE-RSA-AES256-SHA256
DHE-RSA-AES256-SHA ECDHE-ECDSA-CAMELLIA128-SHA256
ECDHE-ECDSA-AES128-GCM-SHA256 ECDHE-ECDSA-AES128-SHA256
ECDHE-ECDSA-AES128-SHA ECDHE-RSA-CAMELLIA128-SHA256
ECDHE-RSA-AES128-GCM-SHA256 ECDHE-RSA-AES128-SHA256 ECDHE-RSA-AES128-SHA

Apache Tomcat

Apache has posted instructions on disabling SSLv3 instructions at http://wiki.apache.org/tomcat/Security/POODLE.

Notifying your users

Add this code to your website to embed our browser SSLv3 test.

<iframe src="https://poodle.io/sslv3test.html" width="100%" frameborder="0" height="75"></iframe>

We are working to post details on how to disable SSLv3 support in additional services. If you have details on how SSLv3 support can be disabled in your product, please email us at poodle-team@umich.edu.