It was reported [1] that Smack (XMPP client library) is vulnerable to MitM attacks with a crafted SSL certificates.
Quote from [1]:
...
Details
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Smack is using Java's `SSLSocket`, which checks the peer certificate
using an `X509TrustManager`, but does not perform hostname verification.
Therefore, it is possible to redirect the traffic between a Smack-using
application and a legitimate XMPP server through the attacker's server,
merely by providing a valid certificate for a domain under the
attacker's control.

In Smack versions 2.2.0 to 3.4.1, a custom `ServerTrustManager`
implementation was used, which was supplied with the connection's server
name, and performed hostname verification. However, it failed to verify
the basicConstraints and nameConstraints of the certificate chain
(CVE-2014-0363, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-0363)
and has been removed in Smack 4.0.0.

Applications using Smack 2.2.0 to 3.4.1 with a custom `TrustManager` did
not benefit from `ServerTrustManager` and are vulnerable as well, unless
their own `TrustManager` implementation explicitly performs hostname
verification.
...

[1]: http://seclists.org/bugtraq/2014/Aug/29