munin-cgi-graph in Munin 2.0 rc4 allows remote attackers to cause a denial of service (disk or memory consumption) via many image requests with large values in the (1) size_x or (2) size_y parameters.
The get_group_tree function in lib/Munin/Master/HTMLConfig.pm in Munin before 2.0.18 allows remote nodes to cause a denial of service (infinite loop and memory consumption in the munin-html process) via crafted multigraph data.