lockmail in maildrop before 1.5.3 does not drop privileges before executing commands, which allows local users to gain privileges via command line arguments.

maildrop: does not drop supplimentary groups when dropping privileges

main.C in maildrop 2.3.0 and earlier, when run by root with the -d option, uses the gid of root for execution of the .mailfilter file in a user's home directory, which allows local users to gain privileges via a crafted file.