The default AFSecurityPolicy.validatesDomainName configuration for AFSSLPinningModeNone in the AFNetworking framework before 2.5.3, as used in the ownCloud iOS Library, disables verification of a server hostname against the domain name in the subject's Common Name (CN) of the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate.

References

• https://nvd.nist.gov/vuln/detail/CVE-2015-3996
• https://github.com/AFNetworking/AFNetworking/issues/2619
• https://github.com/AFNetworking/AFNetworking/releases/tag/2.5.3
• https://owncloud.org/security/advisory/?id=oc-sa-2015-012
• http://www.securityfocus.com/bid/76242