The remote host is missing an update to gnutls26 announced via advisory USN-809-1.

The problem can be corrected by upgrading your system to the following package versions: Ubuntu 6.06 LTS: libgnutls12 1.2.9-2ubuntu1.7 Ubuntu 8.04 LTS: libgnutls13 2.0.4-1ubuntu2.6 Ubuntu 8.10: libgnutls26 2.4.1-1ubuntu0.4 Ubuntu 9.04: libgnutls26 2.4.2-6ubuntu0.1 In general, a standard system upgrade is sufficient to effect the necessary changes. https://secure1.securityspace.com/smysecure/catid.html?in=USN-809-1

Moxie Marlinspike and Dan Kaminsky independently discovered that GnuTLS did not properly handle certificates with NULL characters in the certificate name. An attacker could exploit this to perform a man in the middle attack to view sensitive information or alter encrypted communications. (CVE-2009-2730) Dan Kaminsky discovered GnuTLS would still accept certificates with MD2 hash signatures. As a result, an attacker could potentially create a malicious trusted certificate to impersonate another site. This issue only affected Ubuntu 6.06 LTS and Ubuntu 8.10. (CVE-2009-2409) USN-678-1 fixed a vulnerability and USN-678-2 a regression in GnuTLS. The upstream patches introduced a regression when validating certain certificate chains that would report valid certificates as untrusted. This update fixes the problem, and only affected Ubuntu 6.06 LTS and Ubuntu 8.10 (Ubuntu 8.04 LTS and 9.04 were fixed at an earlier date). In an effort to maintain a strong security stance and address all known regressions, this update deprecates X.509 validation chains using MD2 and MD5 signatures. To accomodate sites which must still use a deprected RSA-MD5 certificate, GnuTLS has been updated to stop looking when it has found a trusted intermediary certificate. This new handling of intermediary certificates is in accordance with other SSL implementations. Original advisory details: Martin von Gagern discovered that GnuTLS did not properly verify certificate chains when the last certificate in the chain was self-signed. If a remote attacker were able to perform a man-in-the-middle attack, this flaw could be exploited to view sensitive information. (CVE-2008-4989)