librsync before 1.0.0 uses a truncated MD4 checksum to match blocks, which makes it easier for remote attackers to modify transmitted data via a birthday attack.
http://lists.fedoraproject.org/pipermail/package-announce/2015-March/151105.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-March/152355.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-March/152366.html
http://lists.opensuse.org/opensuse-updates/2015-10/msg00034.html
http://www.openwall.com/lists/oss-security/2014/07/28/1
http://www.openwall.com/lists/oss-security/2014/08/05/5
http://www.openwall.com/lists/oss-security/2014/10/13/2
https://bugzilla.redhat.com/show_bug.cgi?id=1126712
https://github.com/librsync/librsync/issues/5
https://github.com/librsync/librsync/releases/tag/v1.0.0