From 4c1cbb768b293ea49f9b0eeab2004589d0c2624d Mon Sep 17 00:00:00 2001
From: phrwlk <phrwlk7@gmail.com>
Date: Mon, 9 Feb 2026 22:37:57 +0200
Subject: [PATCH 1/2] fix: clear reference-type elements in Truncate to prevent
 pool memory leak

---
 src/Nethermind/Nethermind.Core/Collections/ArrayListCore.cs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/Nethermind/Nethermind.Core/Collections/ArrayListCore.cs b/src/Nethermind/Nethermind.Core/Collections/ArrayListCore.cs
index 00b95e683953..06a2167b897c 100644
--- a/src/Nethermind/Nethermind.Core/Collections/ArrayListCore.cs
+++ b/src/Nethermind/Nethermind.Core/Collections/ArrayListCore.cs
@@ -228,6 +228,10 @@ public static void Insert(
     public static void Truncate(int newLength, T[] array, ref int count)
     {
         GuardIndex(newLength, count, shouldThrow: true, allowEqualToCount: true);
+        if (RuntimeHelpers.IsReferenceOrContainsReferences<T>() && newLength < count)
+        {
+            Array.Clear(array, newLength, count - newLength);
+        }
         count = newLength;
     }
 

From 019539b02e808b3201d5b7b42f2f41917d6be45d Mon Sep 17 00:00:00 2001
From: phrwlk <phrwlk7@gmail.com>
Date: Tue, 10 Feb 2026 13:23:56 +0200
Subject: [PATCH 2/2] add helper

---
 .../Collections/ArrayListCore.cs               | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/Nethermind/Nethermind.Core/Collections/ArrayListCore.cs b/src/Nethermind/Nethermind.Core/Collections/ArrayListCore.cs
index 06a2167b897c..518fb7512842 100644
--- a/src/Nethermind/Nethermind.Core/Collections/ArrayListCore.cs
+++ b/src/Nethermind/Nethermind.Core/Collections/ArrayListCore.cs
@@ -51,6 +51,15 @@ public static void ClearToCount(T[] array, int count)
         }
     }
 
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static void ClearTail(T[] array, int newCount, int oldCount)
+    {
+        if (RuntimeHelpers.IsReferenceOrContainsReferences<T>() && newCount < oldCount)
+        {
+            Array.Clear(array, newCount, oldCount - newCount);
+        }
+    }
+
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static void Add(
         ArrayPool<T> pool,
@@ -108,9 +117,9 @@ public static void ReduceCount(
             ClearToCount(oldArray, oldCount);
             pool.Return(oldArray);
         }
-        else if (RuntimeHelpers.IsReferenceOrContainsReferences<T>())
+        else
         {
-            Array.Clear(array, newCount, oldCount - newCount);
+            ClearTail(array, newCount, oldCount);
         }
 
         [DoesNotReturn]
@@ -228,10 +237,7 @@ public static void Insert(
     public static void Truncate(int newLength, T[] array, ref int count)
     {
         GuardIndex(newLength, count, shouldThrow: true, allowEqualToCount: true);
-        if (RuntimeHelpers.IsReferenceOrContainsReferences<T>() && newLength < count)
-        {
-            Array.Clear(array, newLength, count - newLength);
-        }
+        ClearTail(array, newLength, count);
         count = newLength;
     }