It was discovered that Kerberos did not properly determine the acceptability of certain checksums. A remote attacker could use certain checksums to alter the prompt message, modify a response to a Key Distribution Center or forge a KRB-SAFE message. It was discovered that Kerberos did not properly determine the acceptability of certain checksums. A remote attacker could use certain checksums to forge GSS tokens or gain privileges. This issue only affected Ubuntu 9.10, 10.04 LTS and 10.10. It was discovered that Kerberos did not reject RC4 key-derivation checksums. An authenticated remote user could use this issue to forge AD-SIGNEDPATH or AD-KDC-ISSUED signatures and possibly gain privileges. This issue only affected Ubuntu 10.04 LTS and 10.10. It was discovered that Kerberos did not properly restrict the use of TGT credentials for armoring TGS requests. A remote authenticated user could use this flaw to impersonate a client. This issue only affected Ubuntu 9.10