Medium [CVE-2026-55892] Denial of Service via crafted spell file

Vim is an open source, command line text editor. Prior to 9.2.0662, the dump_prefixes() function in src/spell.c walks a spell-file prefix trie iteratively with a depth counter while dumping the prefixes that apply to a word.

The counter is bounded only by the trie structure itself; it is never checked against the size of the fixed MAXWLEN-element stack arrays it indexes (prefix[], arridx[], curi[]). A crafted.spl file, loaded when the user dumps the word list, can drive the descent arbitrarily deep, so the function writes past the end of those arrays.

This is a stack out-of-bounds write that corrupts the call frame and crashes the editor. This vulnerability is fixed in 9.2.0662.

A remote attacker could exploit this vulnerability by convincing a user to load a specially crafted spell file. This leads to a Denial of Service (DoS), making the editor unavailable to the user.

A flaw was found in Vim's spell file handling. The dump_prefixes() function in src/spell.c does not validate the depth of the prefix trie against the size of fixed-size stack arrays, allowing a crafted.spl file to cause a stack out-of-bounds write and crash.

Red Hat ships Vim in all RHEL versions and OpenShift CoreOS. Exploitation requires a user to load a malicious spell file and run:spelldump or spelling completion.

Red Hat severity: Moderate — CVSS 5.5 (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H).