How to disable SSLv3

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This article applies to the following ZCS versions.

ZCS 8.0 Article ZCS 8.0 ZCS 8.5 Article ZCS 8.5

How to disable SSLv3

Due to the recent discovery of a new SSL vulnerability (CVE-2014-3566: Poodle SSLv3), this protocol has been considered unsafe. This is a protocol flaw and Zimbra might include patches or configuration changes in future releases. Please check existing Bug

As a workaround, this guide will help you on how to disable SSLv3 with Zimbra. This has been tested on both ZCS 8.0.8 and 8.5.0 releases.



zmprov mcf zimbraMtaSmtpdTlsProtocols '\!SSLv3'


postconf -e smtpd_tls_protocols=\!SSLv3

Run "zmmtactl stop ; zmmtactl start" to force the changes or wait for mailboxd to rewrite Postfix config from LDAP after 2 minutes.

If you are already disabling ciphers by following, please also include SSLv3:


zmprov mcf zimbraMtaSmtpdTlsCiphers high zmprov mcf zimbraMtaSmtpdTlsProtocols '\!SSLv3,\!SSLv2,TLSv1,TLSv2' zmprov mcf zimbraMtaSmtpdTlsMandatoryCiphers high zmprov mcf zimbraMtaSmtpdTlsExcludeCiphers 'aNULL,MD5,DES'


zmlocalconfig -e smtpd_tls_ciphers=high postconf -e smtpd_tls_protocols=\!SSLv3,\!SSLv2,TLSv1,TLSv2 zmlocalconfig -e smtpd_tls_mandatory_ciphers=high postconf -e smtpd_tls_exclude_ciphers=aNULL,MD5,DES

Run "zmmtactl stop ; zmmtactl start" to apply the changes.

Note that smtpd_tls_protocols and smtpd_tls_exclude_ciphers will need to be set after every upgrade as there is no way to preserve them in ZCS 8.0 and previous.



For https and Admin UI:

Please edit /opt/zimbra/conf/nginx/templates/nginx.conf.web.https.default.template

and include the following line under the servers { } configuration:

ssl_protocols TLSv1 TLSv1.1 TLSv1.2;


  1. HTTPS Proxy Default Configuration

server {

   ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
   ${core.ipboth.enabled}listen                  [::]:${web.https.port} default;


Apply the same change at /opt/zimbra/conf/nginx/templates/nginx.conf.web.admin.default.template

If you are using SSO with Client certificates, also edit /opt/zimbra/conf/nginx/templates/nginx.conf.web.sso.default.template.

For imaps and pop3s:

Please edit /opt/zimbra/conf/nginx/templates/nginx.conf.mail.pop3s.default.template


  1. POP3S proxy default configuration

server {

   ssl_protocols TLSv1 TLSv1.1 TLSv1.2;


Apply the same change at /conf/nginx/templates/nginx.conf.mail.imaps.default.template

Restart the proxy servers with: "zmproxyctl stop ; zmproxyctl start"

Jetty (mailboxd)


How to verify if the changes have been done? We should run the following command (as zimbra) for every port using SSL:

openssl s_client -connect `zmhostname`:<port> -ssl3 |grep failure

Example, for port 443: openssl s_client -connect `zmhostname`:443 -ssl3

If it shows a failure, it's good and we don't support SSLv3:

140532971947680:error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure:s3_pkt.c:1275:SSL alert number 40 140532971947680:error:1409E0E5:SSL routines:SSL3_WRITE_BYTES:ssl handshake failure:s3_pkt.c:598:

If you are seeing:

New, TLSv1/SSLv3, Cipher is ECDHE-RSA-AES128-SHA Server public key is 2048 bit Secure Renegotiation IS supported

SSLv3 is still enabled and you need to verify the changes.

Here is a command to verify common ports when using the Zimbra proxy (run this at the proxy):

for p in 993 995 443 ; do echo Port $p ; timeout 3 openssl s_client -connect `zmhostname`:$p -ssl3 |grep failure ; done

If you are proxying adminUI, please add port 9071, 7071 or the port you have configured. If you are proxying SSO requests, please add port 3443.

List of ports: 443 - HTTPS 993 - IMAP-SSL 995 - POP3-SSL 9071 - AdminUI SSL

For Postfix, run the following command at the MTA for the SMTP-SSL port (465):

timeout 3 openssl s_client -connect `zmhostname`:465 -ssl3

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