MIT Kerberos 5 (aka krb5) 1.7.x and 1.8.x through 1.8.3 does not properly determine the acceptability of checksums, which might allow remote attackers to forge GSS tokens, gain privileges, or have unspecified other impact via (1) an unkeyed checksum, (2) an unkeyed PAC checksum, or (3) a KrbFastArmoredReq checksum based on an RC4 key.