A modeline sandbox bypass in Vim allows arbitrary OS command execution when a user opens a crafted file. The complete, guitabtooltip and printheader options are missing the P_MLE flag, allowing a modeline to be executed. Additionally, the mapset() function lacks a check_secure() call, allowing it to be abused from sandboxed expressions.

An attacker who can deliver a crafted file to a victim achieves arbitrary command execution with the privileges of the user running Vim.