--- a/net/minecraft/world/level/block/entity/TileEntityBanner.java
+++ b/net/minecraft/world/level/block/entity/TileEntityBanner.java
@@ -20,6 +20,10 @@
 import net.minecraft.world.level.block.BlockBannerAbstract;
 import net.minecraft.world.level.block.state.IBlockData;
 
+// CraftBukkit start
+import java.util.List;
+// CraftBukkit end
+
 public class TileEntityBanner extends TileEntity implements INamableTileEntity {
 
     public static final int MAX_PATTERNS = 6;
@@ -68,7 +72,7 @@
         this.name = parseCustomNameSafe(nbttagcompound.get("CustomName"), holderlookup_a);
         RegistryOps<NBTBase> registryops = holderlookup_a.<NBTBase>createSerializationContext(DynamicOpsNBT.INSTANCE);
 
-        this.patterns = (BannerPatternLayers) nbttagcompound.read("patterns", BannerPatternLayers.CODEC, registryops).orElse(BannerPatternLayers.EMPTY);
+        this.setPatterns((BannerPatternLayers) nbttagcompound.read("patterns", BannerPatternLayers.CODEC, registryops).orElse(BannerPatternLayers.EMPTY)); // CraftBukkit - apply limits
     }
 
     @Override
@@ -99,7 +103,7 @@
     @Override
     protected void applyImplicitComponents(DataComponentGetter datacomponentgetter) {
         super.applyImplicitComponents(datacomponentgetter);
-        this.patterns = (BannerPatternLayers) datacomponentgetter.getOrDefault(DataComponents.BANNER_PATTERNS, BannerPatternLayers.EMPTY);
+        this.setPatterns((BannerPatternLayers) datacomponentgetter.getOrDefault(DataComponents.BANNER_PATTERNS, BannerPatternLayers.EMPTY)); // CraftBukkit - apply limits
         this.name = (IChatBaseComponent) datacomponentgetter.get(DataComponents.CUSTOM_NAME);
     }
 
@@ -115,4 +119,13 @@
         nbttagcompound.remove("patterns");
         nbttagcompound.remove("CustomName");
     }
+
+    // CraftBukkit start
+    public void setPatterns(BannerPatternLayers bannerpatternlayers) {
+        if (bannerpatternlayers.layers().size() > 20) {
+            bannerpatternlayers = new BannerPatternLayers(List.copyOf(bannerpatternlayers.layers().subList(0, 20)));
+        }
+        this.patterns = bannerpatternlayers;
+    }
+    // CraftBukkit end
 }