From 675cab3074fc7cfada98026ce21de48551c9f834 Mon Sep 17 00:00:00 2001
From: Nanook <188841+Nanook@users.noreply.github.com>
Date: Fri, 7 Feb 2025 22:39:33 +0000
Subject: [PATCH] Fix for Rar4 v20 compression.

---
 src/SharpCompress/Compressors/Rar/UnpackV1/Unpack20.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack20.cs b/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack20.cs
index 809aaf60e..19af8c857 100644
--- a/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack20.cs
+++ b/src/SharpCompress/Compressors/Rar/UnpackV1/Unpack20.cs
@@ -369,7 +369,7 @@ private void CopyString20(int Length, int Distance)
         destUnpSize -= Length;
 
         var DestPtr = unpPtr - Distance;
-        if (DestPtr < PackDef.MAXWINSIZE - 300 && unpPtr < PackDef.MAXWINSIZE - 300)
+        if (DestPtr >= 0 && DestPtr < PackDef.MAXWINSIZE - 300 && unpPtr < PackDef.MAXWINSIZE - 300)
         {
             window[unpPtr++] = window[DestPtr++];
             window[unpPtr++] = window[DestPtr++];