The remote host is missing an update to libicu announced via advisory DSA 1511-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201511-1

Several local vulnerabilities have been discovered in libicu, International Components for Unicode, The Common Vulnerabilities and Exposures project identifies the following problems: CVE-2007-4770 libicu in International Components for Unicode (ICU) 3.8.1 and earlier attempts to process backreferences to the nonexistent capture group zero (aka \0), which might allow context-dependent attackers to read from, or write to, out-of-bounds memory locations, related to corruption of REStackFrames. CVE-2007-4771 Heap-based buffer overflow in the doInterval function in regexcmp.cpp in libicu in International Components for Unicode (ICU) 3.8.1 and earlier allows context-dependent attackers to cause a denial of service (memory consumption) and possibly have unspecified other impact via a regular expression that writes a large amount of data to the backtracking stack. For the stable distribution (etch), these problems have been fixed in version 3.6-2etch1. For the unstable distribution (sid), these problems have been fixed in version 3.8-6. We recommend that you upgrade your libicu package.