diff --git a/Source/msg.cpp b/Source/msg.cpp
index dc9aa5d95..2676cb7a6 100644
--- a/Source/msg.cpp
+++ b/Source/msg.cpp
@@ -34,6 +34,7 @@
 #include "nthread.h"
 #include "objects.h"
 #include "options.h"
+#include "pack.h"
 #include "pfile.h"
 #include "plrmsg.h"
 #include "spells.h"
@@ -45,8 +46,44 @@
 #include "utils/str_cat.hpp"
 #include "utils/utf8.hpp"
 
+#define ValidateField(logValue, condition)                    \
+	do {                                                      \
+		if (!(condition)) {                                   \
+			LogFailedPacket(#condition, #logValue, logValue); \
+			EventFailedPacket(player._pName);                 \
+			return false;                                     \
+		}                                                     \
+	} while (0)
+
+#define ValidateFields(logValue1, logValue2, condition)                                \
+	do {                                                                               \
+		if (!(condition)) {                                                            \
+			LogFailedPacket(#condition, #logValue1, logValue1, #logValue2, logValue2); \
+			EventFailedPacket(player._pName);                                          \
+			return false;                                                              \
+		}                                                                              \
+	} while (0)
+
 namespace devilution {
 
+void EventFailedPacket(const char *playerName)
+{
+	std::string message = fmt::format("Player '{}' sent an invalid packet.", playerName);
+	EventPlrMsg(message);
+}
+
+template <typename T>
+void LogFailedPacket(const char *condition, const char *name, T value)
+{
+	LogDebug("Remote player packet validation failed: ValidateField({}: {}, {})", name, value, condition);
+}
+
+template <typename T1, typename T2>
+void LogFailedPacket(const char *condition, const char *name1, T1 value1, const char *name2, T2 value2)
+{
+	LogDebug("Remote player packet validation failed: ValidateFields({}: {}, {}: {}, {})", name1, value1, name2, value2, condition);
+}
+
 // #define LOG_RECEIVED_MESSAGES
 
 uint8_t gbBufferMsgs;
@@ -964,14 +1001,30 @@ bool IsGItemValid(const TCmdGItem &message)
 	return IsItemAvailable(static_cast<_item_indexes>(SDL_SwapLE16(message.def.wIndx)));
 }
 
-bool IsPItemValid(const TCmdPItem &message)
+bool IsPItemValid(const TCmdPItem &message, const Player &player)
 {
 	const Point position { message.x, message.y };
 
 	if (!InDungeonBounds(position))
 		return false;
 
-	return IsItemAvailable(static_cast<_item_indexes>(SDL_SwapLE16(message.def.wIndx)));
+	auto idx = static_cast<_item_indexes>(SDL_SwapLE16(message.def.wIndx));
+
+	if (idx != IDI_EAR) {
+		uint16_t creationFlags = SDL_SwapLE16(message.item.wCI);
+		uint32_t dwBuff = SDL_SwapLE16(message.item.dwBuff);
+
+		if (idx != IDI_GOLD)
+			ValidateField(creationFlags, IsCreationFlagComboValid(creationFlags));
+		if ((creationFlags & CF_TOWN) != 0)
+			ValidateField(creationFlags, IsTownItemValid(creationFlags, player));
+		else if ((creationFlags & CF_USEFUL) == CF_UPER15)
+			ValidateFields(creationFlags, dwBuff, IsUniqueMonsterItemValid(creationFlags, dwBuff));
+		else
+			ValidateFields(creationFlags, dwBuff, IsDungeonItemValid(creationFlags, dwBuff));
+	}
+
+	return IsItemAvailable(idx);
 }
 
 void PrepareItemForNetwork(const Item &item, TCmdGItem &message)
@@ -1254,7 +1307,7 @@ size_t OnPutItem(const TCmd *pCmd, Player &player)
 
 	if (gbBufferMsgs == 1) {
 		SendPacket(player, &message, sizeof(message));
-	} else if (IsPItemValid(message)) {
+	} else if (IsPItemValid(message, player)) {
 		const Point position { message.x, message.y };
 		bool isSelf = &player == MyPlayer;
 		const int32_t dwSeed = SDL_SwapLE32(message.def.dwSeed);
@@ -1294,7 +1347,7 @@ size_t OnSyncPutItem(const TCmd *pCmd, Player &player)
 
 	if (gbBufferMsgs == 1)
 		SendPacket(player, &message, sizeof(message));
-	else if (IsPItemValid(message)) {
+	else if (IsPItemValid(message, player)) {
 		const int32_t dwSeed = SDL_SwapLE32(message.def.dwSeed);
 		const uint16_t wCI = SDL_SwapLE16(message.def.wCI);
 		const _item_indexes wIndx = static_cast<_item_indexes>(SDL_SwapLE16(message.def.wIndx));
@@ -1950,7 +2003,7 @@ size_t OnDropItem(const TCmd *pCmd, Player &player)
 
 	if (gbBufferMsgs == 1) {
 		SendPacket(player, &message, sizeof(message));
-	} else if (IsPItemValid(message)) {
+	} else if (IsPItemValid(message, player)) {
 		DeltaPutItem(message, { message.x, message.y }, player);
 	}
 
@@ -1963,7 +2016,7 @@ size_t OnSpawnItem(const TCmd *pCmd, Player &player)
 
 	if (gbBufferMsgs == 1) {
 		SendPacket(player, &message, sizeof(message));
-	} else if (IsPItemValid(message)) {
+	} else if (IsPItemValid(message, player)) {
 		if (player.isOnActiveLevel() && &player != MyPlayer) {
 			SyncDropItem(message);
 		}
diff --git a/Source/pack.cpp b/Source/pack.cpp
index 7fe7c8ab9..e9039b8fd 100644
--- a/Source/pack.cpp
+++ b/Source/pack.cpp
@@ -80,6 +80,8 @@ bool hasMultipleFlags(uint16_t flags)
 	return (flags & (flags - 1)) > 0;
 }
 
+} // namespace
+
 bool IsCreationFlagComboValid(uint16_t iCreateInfo)
 {
 	iCreateInfo = iCreateInfo & ~CF_LEVEL;
@@ -198,8 +200,6 @@ bool RecreateHellfireSpellBook(const Player &player, const ItemNetPack &packedIt
 	return true;
 }
 
-} // namespace
-
 void PackItem(ItemPack &packedItem, const Item &item, bool isHellfire)
 {
 	packedItem = {};
@@ -562,7 +562,7 @@ bool UnPackNetPlayer(const PlayerNetPack &packed, Player &player)
 	ValidateFields(packed.pClass, packed.pBaseDex, packed.pBaseDex <= player.GetMaximumAttributeValue(CharacterAttribute::Dexterity));
 	ValidateFields(packed.pClass, packed.pBaseVit, packed.pBaseVit <= player.GetMaximumAttributeValue(CharacterAttribute::Vitality));
 
-	ValidateField(packed._pNumInv, packed._pNumInv < InventoryGridCells);
+	ValidateField(packed._pNumInv, packed._pNumInv <= InventoryGridCells);
 
 	player.setCharacterLevel(packed.pLevel);
 	player.position.tile = position;
diff --git a/Source/pack.h b/Source/pack.h
index 9cefabbff..5ff70a1c5 100644
--- a/Source/pack.h
+++ b/Source/pack.h
@@ -142,6 +142,10 @@ struct PlayerNetPack {
 };
 #pragma pack(pop)
 
+bool IsCreationFlagComboValid(uint16_t iCreateInfo);
+bool IsTownItemValid(uint16_t iCreateInfo, const Player &player);
+bool IsUniqueMonsterItemValid(uint16_t iCreateInfo, uint32_t dwBuff);
+bool IsDungeonItemValid(uint16_t iCreateInfo, uint32_t dwBuff);
 void PackPlayer(PlayerPack &pPack, const Player &player);
 void UnPackPlayer(const PlayerPack &pPack, Player &player);
 void PackNetPlayer(PlayerNetPack &packed, const Player &player);
diff --git a/test/pack_test.cpp b/test/pack_test.cpp
index 7e45a927c..6d706b487 100644
--- a/test/pack_test.cpp
+++ b/test/pack_test.cpp
@@ -1038,7 +1038,7 @@ TEST_F(NetPackTest, UnPackNetPlayer_invalid_baseVit)
 
 TEST_F(NetPackTest, UnPackNetPlayer_invalid_numInv)
 {
-	MyPlayer->_pNumInv = InventoryGridCells;
+	MyPlayer->_pNumInv = InventoryGridCells + 1;
 	ASSERT_FALSE(TestNetPackValidation());
 }