CVE-2026-52859 vim CVE debrief

Who should care

Users of Vim, a command-line text editor, should be aware of this vulnerability. Specifically, those who render program output inside a :terminal window are at risk.

Technical summary

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.

Defensive priority

MEDIUM

Recommended defensive actions

• Update Vim to version 9.2.0565 or later.
• Avoid rendering untrusted program output inside a :terminal window.

Evidence notes

The CVE-2026-52859 vulnerability was patched in Vim version 9.2.0565. The vulnerability has a CVSS score of 6.9 and is classified as MEDIUM severity.

Official resources