From: Markus Koschany <apo@debian.org>
Date: Mon, 31 Oct 2022 14:50:16 +0100
Subject: CVE-2022-1616

Origin: https://github.com/vim/vim/commit/d88934406c5375d88f8f1b65331c9f0cab68cc6c
---
 src/ex_docmd.c               |  4 +++-
 src/testdir/test_cmdline.vim | 12 ++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -3116,7 +3116,7 @@ append_command(char_u *cmd)
 
     STRCAT(IObuff, ": ");
     d = IObuff + STRLEN(IObuff);
-    while (*s != NUL && d - IObuff < IOSIZE - 7)
+    while (*s != NUL && d - IObuff + 5 < IOSIZE)
     {
 	if (enc_utf8 ? (s[0] == 0xc2 && s[1] == 0xa0) : *s == 0xa0)
 	{
@@ -3124,6 +3124,8 @@ append_command(char_u *cmd)
 	    STRCPY(d, "<a0>");
 	    d += 4;
 	}
+	else if (d - IObuff + (*mb_ptr2len)(s) + 1 >= IOSIZE)
+	    break;
 	else
 	    MB_COPY_CHAR(s, d);
     }
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -609,4 +609,16 @@ func Test_cmdline_overstrike()
   let &encoding = encoding_save
 endfunc
 
+" this was going over the end of IObuff
+func Test_report_error_with_composing()
+  let caught = 'no'
+  try
+    exe repeat('0', 987) . "0\xdd\x80\xdd\x80\xdd\x80\xdd\x80"
+  catch /E492:/
+    let caught = 'yes'
+ endtry
+  call assert_equal('yes', caught)
+endfunc
+
+
 set cpo&