getchar.c in Vim before 8.1.1365 and Neovim before 0.3.6 allows remote attackers to execute arbitrary OS commands via the :source! command in a modeline, as demonstrated by execute in Vim, and assert_fails or nvim_input in Neovim.

vim before patch 8.0.0322 does not properly validate values for tree length when handling a spell file, which may result in an integer overflow at a memory allocation site and a resultant buffer overflow.