Isync 0.4 before 1.0.6, 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.
Gentoo Linux Security Advisory 201310-2 - A vulnerability in isync could allow remote attackers to perform man-in-the-middle attacks. Versions less than 1.0.6 are affected.