From ea20c181c76ef339b5cf1ae02ce3f7593c57d14d Mon Sep 17 00:00:00 2001
From: Christian Brabandt <cb@256bit.org>
Date: Sun, 17 May 2026 19:39:24 +0000
Subject: [PATCH] patch 9.2.0496: [security]: Code Injection in cucumber
 filetype plugin

Problem:  [security]: Code Injection in cucumber filetype plugin
          (Christopher Lusk)
Solution: Use rubys Regexp.new() with the untrusted pattern

Github Security Advisory:
https://github.com/vim/vim/security/advisories/GHSA-4473-94jm-w5x9

Signed-off-by: Christian Brabandt <cb@256bit.org>
---
 runtime/ftplugin/cucumber.vim |  3 ++-
 src/testdir/test_filetype.vim | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/runtime/ftplugin/cucumber.vim b/runtime/ftplugin/cucumber.vim
index f4848d1..3361f1d 100644
--- a/runtime/ftplugin/cucumber.vim
+++ b/runtime/ftplugin/cucumber.vim
@@ -96,7 +96,8 @@ function! s:stepmatch(receiver,target)
   catch
   endtry
   if has("ruby") && pattern !~ '\\\@<!#{'
-    ruby VIM.command("return #{if (begin; Kernel.eval('/'+VIM.evaluate('pattern')+'/'); rescue SyntaxError; end) === VIM.evaluate('a:target') then 1 else 0 end}")
+    " Use Regexp.new, so the pattern stays untrusted data and cannot inject Ruby
+    ruby VIM.command("return #{if (begin; Regexp.new(VIM.evaluate('pattern')); rescue RegexpError; end) === VIM.evaluate('a:target') then 1 else 0 end}")
   else
     return 0
   endif
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index 62dbc74..e484d2f 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -595,3 +595,36 @@ func Test_script_detection()
   filetype off
 endfunc
 
+func Test_cucumber_code_injection()
+  if !has('ruby')
+    return
+  endif
+  filetype plugin on
+
+  call mkdir('Xcucu/features/step_definitions', 'p')
+  call writefile([
+        \ 'Feature: demo',
+        \ '  Scenario: trigger',
+        \ '    Given xyzzy',
+        \ ], 'Xcucu/features/test.feature')
+  let marker = getcwd() . '/Xcucu/MARKER'
+  " Malicious step: terminates the regex literal, injects Ruby system(),
+  " comments the trailing slash.  With the fix, the pattern is passed to
+  " Regexp.new() instead of Kernel.eval() and the payload is inert.
+  call writefile([
+        \ 'Given /xyzzy/; system("touch ' . marker . '"); #/ do',
+        \ 'end',
+        \ ], 'Xcucu/features/step_definitions/poc.rb')
+
+  new Xcucu/features/test.feature
+  call assert_equal('cucumber', &filetype)
+  call cursor(3, 1)
+  " Triggers s:jump -> s:steps -> s:stepmatch on every discovered step,
+  " including the malicious one.  Suppress preview and error messages.
+  silent! normal [d
+  call assert_false(filereadable(marker), 'Ruby injection executed')
+  bwipe!
+  call delete('Xcucu', 'rf')
+  filetype plugin off
+endfunc
+
-- 
2.52.0