OpenVPN, when using a 64-bit block cipher, makes it easier for remote attackers to obtain cleartext data via a birthday attack against a long-duration encrypted session, as demonstrated by an HTTP-over-OpenVPN session using Blowfish in CBC mode, aka a “Sweet32” attack.
www-01.ibm.com/support/docview.wss?uid=nas8N1021697
www-01.ibm.com/support/docview.wss?uid=swg21991482
www-01.ibm.com/support/docview.wss?uid=swg21995039
www.securityfocus.com/bid/92631
www.securitytracker.com/id/1036695
cert-portal.siemens.com/productcert/pdf/ssa-556833.pdf
community.openvpn.net/openvpn/wiki/SWEET32
h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05369403
security.gentoo.org/glsa/201611-02
sweet32.info/