The Wocky module in Telepathy Gabble before 0.16.6 and 0.17.x before 0.17.4, when connecting to a "legacy Jabber server," does not properly enforce the WockyConnector:tls-required flag, which allows remote attackers to bypass TLS verification and perform a man-in-the-middle attacks.
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.