The remote host is missing an update to rsync announced via advisory DSA 1360-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201360-1

Sebastian Krahmer discovered that rsync, a fast remote file copy program, contains an off-by-one error which might allow remote attackers to execute arbitary code via long directory names. For the stable distribution (etch), this problem has been fixed in version 2.6.9-2etch1. For the old stable distribution (sarge), this problem is not presnt. For the unstable distribution (sid) this problem will be fixed soon. We recommend that you upgrade your rsync package.