Mandriva Linux Security Advisory 2015-204 – librsync before 1.0.0 used a truncated MD4 strong check sum to match blocks. However, MD4 is not cryptographically strong. It’s possible that an attacker who can control the contents of one part of a file could use it to control other regions of the file, if it’s transferred using librsync/rdiff. The change to fix this is not backward compatible with older versions of librsync. Backward compatibility can be obtained using the new rdiff sig –hash=md4 option or through specifying the signature magic in the API, but this should not be used when either the old or new file contain untrusted data. Also, any applications that use the librsync library will need to be recompiled against the updated library. The rdiff-backup packages have been rebuilt for this reason.