Medium [CVE-2026-59857] Denial of Service via out-of-bounds write in spell sound-folding

Vim is an open source, command line text editor.

Prior to 9.2.0725, the single-byte branch of spell_soundfold_sal() in src/spell.c translates a word through a spell file's SAL sound-folding rules into a caller-owned result buffer, but its result writes are guarded with reslen < MAXWLEN, allowing reslen to reach MAXWLEN before res[reslen] = NUL writes one byte past the end of the MAXWLEN-element stack buffer.

A boundary-length word passed to soundfold(), or reached via sound-based spell suggestion while a SAL-based spell language is active under a non-multibyte 8-bit encoding, can corrupt the eval_soundfold() stack frame and crash the editor. This issue is fixed in version 9.2.0725.

An out-of-bounds write vulnerability in Vim's spell_soundfold_sal() function allows an attacker to corrupt memory and crash the editor (Denial of Service) by supplying a specially crafted word during spell sound-folding. This Moderate impact flaw in Vim's spell sound-folding feature can lead to a denial of service.

This vulnerability primarily affects interactive users of the Vim text editor. 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).

Weakness: CWE-787.

Affected products named by the advisory: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat Hardened Images; and 5 more.