Moodle 2.0.x before 2.0.3 allows remote authenticated users to cause a denial of service (invalid database records) via a series of crafted comments operations.
message/refresh.php in Moodle 1.9.x before 1.9.14 allows remote authenticated users to cause a denial of service (infinite request loop) via a URL that specifies a zero wait time for message refreshing.
Algorithmic complexity vulnerability in Moodle 1.9.x before 1.9.19, 2.0.x before 2.0.10, 2.1.x before 2.1.7, and 2.2.x before 2.2.4 allows remote authenticated users to cause a denial of service (CPU consumption) by using the advanced-search feature on a database activity that has many records.