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GHSA-r5v6-q6j8-8qw2

CVE Information

Arbitrary Code Execution via Shell Keyword Lookup in Vim < 9.2.0839

Date: 23.07.2026 Severity: Medium CVE: requested, not yet assigned CWE: Improper Neutralization of Special Elements used in an OS Command (CWE-78)

Summary

The shell filetype plugins runtime/ftplugin/sh.vim and runtime/ftplugin/zsh.vim install a buffer-local keywordprg that interpolates its argument into a bash -c or zsh -c command without shell escaping. Because a keywordprg beginning with : is escaped with fnameescape(), which does not neutralize shell metacharacters, and because K in Visual mode passes the whole selection verbatim, a crafted line in a shell script can execute arbitrary commands when the user selects it and presses K. runtime/ftplugin/ps1.vim is affected in the same way through PowerShell.

Description

When a buffer's filetype resolves to bash, zsh or PowerShell, the bundled filetype plugin defines a keyword lookup command and points keywordprg at it, for example:

command! -buffer -nargs=1 ShKeywordPrg silent exe
  \ ':hor term bash -c "help "<args>" 2>/dev/null || man "<args>""'
setlocal keywordprg=:ShKeywordPrg

For a keywordprg that starts with :, Vim escapes the argument of K with vim_strsave_fnameescape() (src/normal.c), which uses PATH_ESC_CHARS (src/vim.h). That set omits the shell metacharacters ;, &, (, ) and >; those appear only in SHELL_ESC_CHARS, which is used exclusively for a keywordprg that is not an Ex command. The filetype plugin adds no escaping of its own, so these characters reach the inner bash -c unchanged and terminate the intended command.

In Visual mode, K passes the entire selection rather than the keyword under the cursor, so shell metacharacters are preserved. In Normal mode the argument is restricted to 'iskeyword' characters, which excludes these metacharacters, and the issue does not arise.

The same pattern applies to runtime/ftplugin/zsh.vim, which builds a zsh -c command, and to runtime/ftplugin/ps1.vim, which passes the argument to PowerShell via -Command.

Impact

Arbitrary operating-system command execution in the context of the user running Vim. Exploitation requires:

  • Vim with filetype plugins enabled
  • the buffer's filetype resolving to sh, bash, zsh or PowerShell
  • the victim opening a crafted file, selecting the crafted line in Visual mode and invoking the keyword lookup with K.

The severity is rated Medium because Normal-mode K is not affected and exploitation requires the victim to deliberately select the crafted text in Visual mode and invoke the keyword lookup; the bug does not fire on file-open alone.

Acknowledgements

The Vim project would like to thank Github user @manus-use for reporting the issue.

References

The issue has been fixed as of Vim patch v9.2.0839.