The remote host is missing an update to rsync announced via advisory DSA 538-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20538-1

The rsync developers have discoverd a security related problem in rsync, a fast remote file copy program, which offers an attacker to access files outside of the defined directory. To exploit this path-sanitizing bug, rsync has to run in daemon mode with the chroot option being disabled. It does not affect the normal send/receive filenames that specify what files should be transferred. It does affect certain option paths that cause auxilliary files to be read or written. For the stable distribution (woody) this problem has been fixed in version 2.5.5-0.6. For the unstable distribution (sid) this problem has been fixed in version 2.6.2-3. We recommend that you upgrade your rsync package.