The remote host is missing an update to python-crypto announced via advisory DSA 1726-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201726-1

Mike Wiacek discovered that a buffer overflow in the ARC2 implementation of Python Crypto, a collection of cryptographic algorithms and protocols for Python allows denial of service and potentially the execution of arbitrary code. For the stable distribution (lenny), this problem has been fixed in version 2.0.1+dfsg1-2.3+lenny0. Due to a technical limitation in the Debian archive management scripts the update for the old stable distribution (etch) cannot be released synchronously. It will be fixed in version 2.0.1+dfsg1-1.2+etch0 soon. For the unstable distribution (sid), this problem will be fixed soon. We recommend that you upgrade your python-crypto package.