Vim < v9.1.0648 has a double-free in dialog_changed()

Vulnerability Description

Vim is an open source command line text editor. double-free in dialog_changed() in Vim < v9.1.0648. When abandoning a buffer, Vim may ask the user what to do with the modified buffer. If the user wants the changed buffer to be saved, Vim may create a new Untitled file, if the buffer did not have a name yet. However, when setting the buffer name to Unnamed, Vim will falsely free a pointer twice, leading to a double-free and possibly later to a heap-use-after-free, which can lead to a crash. The issue has been fixed as of Vim patch v9.1.0648.

References

• https://github.com/vim/vim/security/advisories/GHSA-46pw-v7qw-xc2f
• https://github.com/vim/vim/commit/b29f4abcd4b3382fa746edd1d0562b7b48c