Out-of-bounds write in Vim - CVE-2026-55892

Detailed vulnerability description

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to out-of-bounds write in the dump_prefixes() function in src/spell.c when parsing a crafted .spl spell file during word list dumping. A remote attacker can supply a crafted spell file to cause a denial of service.

User interaction is required: spell checking must be enabled and the user must dump the word list, such as via :spelldump or spelling completion.

How to mitigate CVE-2026-55892

Sources

• https://github.com/vim/vim/security/advisories/GHSA-qm9w-fmpj-879h
• https://github.com/vim/vim/commit/8325b193bba5f01e7a7d8241f