CVE-2025-26603

Date: February 18, 2025

Vim is a greatly improved version of the good old UNIX editor Vi. Vim allows to redirect screen messages using the ":redir" ex command to register, variables and files. It also allows to show the contents of registers using the ":registers" or ":display" ex command. When redirecting the output of ":display" to a register, Vim will free the register content before storing the new content in the register. Now when redirecting the ":display" command to a register that is being displayed, Vim will free the content while shortly afterwards trying to access it, which leads to a use-after-free. Vim pre 9.1.1115 checks in the ex_display() function, that it does not try to redirect to a register while displaying this register at the same time. However this check is not complete, and so Vim does not check the "+" and "*" registers (which typically donate the X11/clipboard registers, and when a clipboard connection is not possible will fall back to use register 0 instead. In Patch 9.1.1115 Vim will therefore skip outputting to register zero when trying to redirect to the clipboard registers "*" or "+". Users are advised to upgrade. There are no known workarounds for this vulnerability.