Race condition in the XMPP library in Smack before 4.1.9, when the SecurityMode.required TLS setting has been set, allows man-in-the-middle attackers to bypass TLS protections and trigger use of cleartext for client authentication by stripping the "starttls" feature from a server response.

The Ignite Realtime Smack XMPP API 4.x before 4.0.2, and 3.x and 2.x when a custom SSLContext is used, does not verify that the server hostname matches a domain name in the subject's Common Name (CN) or subjectAltName field of the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate.

The ServerTrustManager component in the Ignite Realtime Smack XMPP API before 4.0.0-rc1 does not verify basicConstraints and nameConstraints in X.509 certificate chains from SSL servers, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information via a crafted certificate chain.

The ParseRoster component in the Ignite Realtime Smack XMPP API before 4.0.0-rc1 does not verify the from attribute of a roster-query IQ stanza, which allows remote attackers to spoof IQ responses via a crafted attribute.