The cloud controller (aka CLC) component in Eucalyptus 3.3.x and 3.4.x before 3.4.2, when the dns.recursive.enabled setting is used, allows remote attackers to cause a denial of service (traffic amplification) via spoofed DNS queries.
Eucalyptus 3.0.0 through 4.0.1, when the log level is set to DEBUG or lower, logs user and system passwords, which allows local users to obtain sensitive information by reading the cloud log files.