diff --git a/Source/Core/Core/IOS/ES/Formats.cpp b/Source/Core/Core/IOS/ES/Formats.cpp
index 49ae0e3918..97eba84154 100644
--- a/Source/Core/Core/IOS/ES/Formats.cpp
+++ b/Source/Core/Core/IOS/ES/Formats.cpp
@@ -57,6 +57,11 @@ bool Content::IsShared() const
   return (type & 0x8000) != 0;
 }
 
+bool IsValidTMDSize(size_t size)
+{
+  return size <= 0x49e4;
+}
+
 TMDReader::TMDReader(const std::vector<u8>& bytes) : m_bytes(bytes)
 {
 }
diff --git a/Source/Core/Core/IOS/ES/Formats.h b/Source/Core/Core/IOS/ES/Formats.h
index 0c43809b52..e90cb089b4 100644
--- a/Source/Core/Core/IOS/ES/Formats.h
+++ b/Source/Core/Core/IOS/ES/Formats.h
@@ -130,6 +130,8 @@ struct Ticket
 static_assert(sizeof(Ticket) == 0x2A4, "Ticket has the wrong size");
 #pragma pack(pop)
 
+bool IsValidTMDSize(size_t size);
+
 class TMDReader final
 {
 public:
diff --git a/Source/Core/Core/IOS/ES/TitleManagement.cpp b/Source/Core/Core/IOS/ES/TitleManagement.cpp
index 79b625ce59..487b799d99 100644
--- a/Source/Core/Core/IOS/ES/TitleManagement.cpp
+++ b/Source/Core/Core/IOS/ES/TitleManagement.cpp
@@ -91,6 +91,9 @@ IPCCommandResult ES::ImportTmd(Context& context, const IOCtlVRequest& request)
   if (!request.HasNumberOfValidVectors(1, 0))
     return GetDefaultReply(ES_EINVAL);
 
+  if (!IOS::ES::IsValidTMDSize(request.in_vectors[0].size))
+    return GetDefaultReply(ES_EINVAL);
+
   std::vector<u8> tmd(request.in_vectors[0].size);
   Memory::CopyFromEmu(tmd.data(), request.in_vectors[0].address, request.in_vectors[0].size);
   return GetDefaultReply(ImportTmd(context, tmd));
@@ -131,6 +134,9 @@ IPCCommandResult ES::ImportTitleInit(Context& context, const IOCtlVRequest& requ
   if (!request.HasNumberOfValidVectors(4, 0))
     return GetDefaultReply(ES_EINVAL);
 
+  if (!IOS::ES::IsValidTMDSize(request.in_vectors[0].size))
+    return GetDefaultReply(ES_EINVAL);
+
   std::vector<u8> tmd(request.in_vectors[0].size);
   Memory::CopyFromEmu(tmd.data(), request.in_vectors[0].address, request.in_vectors[0].size);
   return GetDefaultReply(ImportTitleInit(context, tmd));
diff --git a/Source/Core/DiscIO/VolumeWad.cpp b/Source/Core/DiscIO/VolumeWad.cpp
index f170abdd47..86932f897b 100644
--- a/Source/Core/DiscIO/VolumeWad.cpp
+++ b/Source/Core/DiscIO/VolumeWad.cpp
@@ -41,7 +41,7 @@ CVolumeWAD::CVolumeWAD(std::unique_ptr<IBlobReader> reader) : m_reader(std::move
   m_opening_bnr_offset =
       m_tmd_offset + Common::AlignUp(m_tmd_size, 0x40) + Common::AlignUp(m_data_size, 0x40);
 
-  if (m_tmd_size > 1024 * 1024 * 4)
+  if (!IOS::ES::IsValidTMDSize(m_tmd_size))
   {
     ERROR_LOG(DISCIO, "TMD is too large: %u bytes", m_tmd_size);
     return;
diff --git a/Source/Core/DiscIO/VolumeWiiCrypted.cpp b/Source/Core/DiscIO/VolumeWiiCrypted.cpp
index c2826c6515..5e088a9422 100644
--- a/Source/Core/DiscIO/VolumeWiiCrypted.cpp
+++ b/Source/Core/DiscIO/VolumeWiiCrypted.cpp
@@ -81,13 +81,11 @@ CVolumeWiiCrypted::CVolumeWiiCrypted(std::unique_ptr<IBlobReader> reader)
       if (!m_pReader->ReadSwapped(partition_offset + 0x2a8, &tmd_address))
         continue;
       tmd_address <<= 2;
-      if (tmd_size > 1024 * 1024 * 4)
+      if (!IOS::ES::IsValidTMDSize(tmd_size))
       {
-        // The size is checked so that a malicious or corrupt ISO
-        // can't force Dolphin to allocate up to 4 GiB of memory.
-        // 4 MiB should be much bigger than the size of TMDs and much smaller
-        // than the amount of RAM in a computer that can run Dolphin.
-        PanicAlert("TMD > 4 MiB");
+        // This check is normally done by ES in ES_DiVerify, but that would happen too late
+        // (after allocating the buffer), so we do the check here.
+        PanicAlert("Invalid TMD size");
         continue;
       }
       std::vector<u8> tmd_buffer(tmd_size);