runtime(zip): also block single leading slash and absolute paths in Extract

zip#Write(): the Windows path check did not match a single leading
slash (/path), which resolves to the current drive root on Windows.
Simplify the regex to match any leading slash or backslash.

zip#Extract(): add absolute path checks for both Unix and Windows,
matching the existing checks in zip#Write().

closes: #19976

Signed-off-by: q1uf3ng <glna9@protonmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

diff --git a/runtime/autoload/zip.vim b/runtime/autoload/zip.vim
index 6a2d6daa3efa65ce17349d669b5589e5de9ec1cf..aad548239a266cff5f2e0687b9bb76d45a59397d 100644 (file)
--- a/runtime/autoload/zip.vim
+++ b/runtime/autoload/zip.vim
@@ -23,6 +23,7 @@
 " 2026 Apr 01 by Vim Project: Detect more path traversal attacks
 " 2026 Apr 05 by Vim Project: Detect more path traversal attacks
 " 2026 Apr 14 by Vim Project: Detect more path traversal attacks on Windows
+" 2026 Apr 15 by Vim Project: Detect more path traversal attacks on Windows
 " License:     Vim License  (see vim's :help license)
 " Copyright:   Copyright (C) 2005-2019 Charles E. Campbell {{{1
 "              Permission is hereby granted to use and distribute this code,
@@ -406,8 +407,8 @@ fun! zip#Write(fname)
   else
     let zipfile = substitute(a:fname,'^.\{-}zipfile://\(.\{-}\)::[^\\].*$','\1','')
     let fname   = substitute(a:fname,'^.\{-}zipfile://.\{-}::\([^\\].*\)$','\1','')
-    " fname should not start with drive leter or a UNC path
-    if fname =~ '^\%(\%(\a:[\\/]\)\|[\\/]\{2}\)'
+    " fname should not start with drive letter, UNC path, or leading slash
+    if fname =~ '^\%(\a:[\\/]\|[\\/]\)'
       call s:Mess('Error', "***error*** (zip#Write) Path Traversal Attack detected, not writing!")
       call s:ChgDir(curdir,s:WARNING,"(zip#Write) unable to return to ".curdir."!")
       return
@@ -505,6 +506,18 @@ fun! zip#Extract()
     call s:Mess('Error', "***error*** (zip#Browse) Path Traversal Attack detected, not extracting!")
     return
   endif
+  " block absolute paths
+  if has("unix")
+    if fname =~ '^/'
+      call s:Mess('Error', "***error*** (zip#Extract) Path Traversal Attack detected, not extracting!")
+      return
+    endif
+  else
+    if fname =~ '^\%(\a:[\\/]\|[\\/]\)'
+      call s:Mess('Error', "***error*** (zip#Extract) Path Traversal Attack detected, not extracting!")
+      return
+    endif
+  endif
   if filereadable(fname)
     call s:Mess('Error', "***error*** (zip#Extract) <" .. fname .."> already exists in directory, not overwriting!")
     return