Heap-based buffer overflow in Vim - CVE-2026-28420

Detailed vulnerability description

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to a boundary error within the handle_pushline() function in src/terminal.c processing maximum combining characters from Unicode supplementary planes. A remote attacker can trick the victim into copying a specially crafted string into the :terminal buffer, trigger a heap-based buffer overflow and execute arbitrary code on the target system.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

How to mitigate CVE-2026-28420

Sources

• https://github.com/vim/vim/security/advisories/GHSA-rvj2-jrf9-2phg
• https://github.com/vim/vim/commit/bb6de2105b160e729c34063