diff --git a/Source/Core/DiscIO/NANDImporter.cpp b/Source/Core/DiscIO/NANDImporter.cpp
index 4477621984..5ef1d68c4b 100644
--- a/Source/Core/DiscIO/NANDImporter.cpp
+++ b/Source/Core/DiscIO/NANDImporter.cpp
@@ -129,7 +129,8 @@ bool NANDImporter::ExtractFiles()
   constexpr u16 CLUSTER_CHAIN_END = 0xFFFB;
   m_progress_cur = 0;
   m_progress_max = std::ranges::count(m_superblock->fat, CLUSTER_CHAIN_END);
-  return ProcessEntry(0, "");
+  std::bitset<FSTEntryCount> visited;
+  return ProcessEntry(0, "", &visited);
 }
 
 std::string NANDImporter::GetPath(const NANDFSTEntry& entry, const std::string& parent_path)
@@ -138,7 +139,8 @@ std::string NANDImporter::GetPath(const NANDFSTEntry& entry, const std::string&
   return parent_path + '/' + Common::EscapeFileName(name);
 }
 
-bool NANDImporter::ProcessEntry(u16 entry_number, const std::string& parent_path)
+bool NANDImporter::ProcessEntry(u16 entry_number, const std::string& parent_path,
+                                std::bitset<FSTEntryCount>* visited)
 {
   while (entry_number != 0xffff)
   {
@@ -148,6 +150,13 @@ bool NANDImporter::ProcessEntry(u16 entry_number, const std::string& parent_path
       return false;
     }
 
+    if ((*visited)[entry_number])
+    {
+      ERROR_LOG_FMT(DISCIO, "FST entry number {} visited multiple times", entry_number);
+      return false;
+    }
+
+    (*visited)[entry_number] = true;
     const NANDFSTEntry entry = m_superblock->fst[entry_number];
 
     const std::string path = entry_number == 0 ? parent_path : GetPath(entry, parent_path);
@@ -165,7 +174,7 @@ bool NANDImporter::ProcessEntry(u16 entry_number, const std::string& parent_path
     else if (type == Type::Directory)
     {
       File::CreateDir(m_nand_root + path);
-      if (!ProcessEntry(entry.sub, path))
+      if (!ProcessEntry(entry.sub, path, visited))
         return false;
     }
     else
diff --git a/Source/Core/DiscIO/NANDImporter.h b/Source/Core/DiscIO/NANDImporter.h
index f22f043709..6851466f66 100644
--- a/Source/Core/DiscIO/NANDImporter.h
+++ b/Source/Core/DiscIO/NANDImporter.h
@@ -4,6 +4,7 @@
 #pragma once
 
 #include <array>
+#include <bitset>
 #include <functional>
 #include <memory>
 #include <string>
@@ -59,13 +60,14 @@ public:
   };
   static_assert(sizeof(NANDFSTEntry) == 0x20, "Wrong size");
 
+  static constexpr u16 FSTEntryCount = 0x17FF;
   struct NANDSuperblock
   {
     std::array<char, 4> magic;  // "SFFS"
     Common::BigEndianValue<u32> version;
     Common::BigEndianValue<u32> unknown;
     std::array<Common::BigEndianValue<u16>, 0x8000> fat;
-    std::array<NANDFSTEntry, 0x17FF> fst;
+    std::array<NANDFSTEntry, FSTEntryCount> fst;
     std::array<u8, 0x14> pad;
   };
   static_assert(sizeof(NANDSuperblock) == 0x40000, "Wrong size");
@@ -78,7 +80,8 @@ private:
   bool ExtractFiles();
   std::string GetPath(const NANDFSTEntry& entry, const std::string& parent_path);
   std::string FormatDebugString(const NANDFSTEntry& entry);
-  bool ProcessEntry(u16 entry_number, const std::string& parent_path);
+  bool ProcessEntry(u16 entry_number, const std::string& parent_path,
+                    std::bitset<FSTEntryCount>* visited);
   std::vector<u8> GetEntryData(const NANDFSTEntry& entry) const;
   void ExportKeys();