On June 5, 2014 the OpenSSL project released a security advisory. CVE-2014-0224 can allow for a man-in-the-middle (MITM) attack to be carried out between a vulnerable client and vulnerable server. According to OpenSSL, an attacker using a carefully crafted handshake can force the use of weak keying material in OpenSSL SSL/TLS clients and servers. This can be exploited by a Man-in-the-middle (MITM) attack where the attacker can decrypt and modify traffic from the attacked client and server.
The attack can only be performed between a vulnerable client *and* server. OpenSSL clients are vulnerable in all versions of OpenSSL. Servers are only known to be vulnerable in OpenSSL 1.0.1 and 1.0.2-beta1. Users of OpenSSL servers earlier than 1.0.1 are advised to upgrade as a precaution.
It is important to note that Zimbra does not use DTLS nor do we have SSL_MODE_RELEASE_BUFFERS enabled. The impact to Zimbra Collaboration Server is as follows:
- ZCS 6 is not affected
- ZCS 7 is not affected
- ZCS 8 is affected
Specifically, nginx, postfix and OpenLDAP all link to OpenSSL shipped in ZCS8. Other components in the ZCS package also link to the openssl libraries, but the above three are the potentially Internet-facing services that would be attackable. All versions of ZCS8 as released today are vulnerable. ZCS7 is not vulnerable because it uses OpenSSL 1.0.0, which is not vulnerable.