diff --git a/Core/GameEngine/Include/Common/FileSystem.h b/Core/GameEngine/Include/Common/FileSystem.h
index 546242d32a..51bf9153ca 100644
--- a/Core/GameEngine/Include/Common/FileSystem.h
+++ b/Core/GameEngine/Include/Common/FileSystem.h
@@ -53,6 +53,8 @@
 
 #include <Utility/hash_map_adapter.h>
 
+#include "mutex.h"
+
 //----------------------------------------------------------------------------
 //           Forward References
 //----------------------------------------------------------------------------
@@ -128,6 +130,10 @@ struct FileInfo {
 // TheSuperHackers @feature xezon 23/08/2025 Implements file instance access.
 // Can be used to access different versions of files in different archives under the same name.
 // Instance 0 refers to the top file that shadows all other files under the same name.
+// 
+// TheSuperHackers @bugfix xezon 26/10/2025 Adds a mutex to the file exist map to try prevent
+// application hangs during level load after the file exist map was corrupted because of writes
+// from multiple threads.
 //===============================
 class FileSystem : public SubsystemInterface
 {
@@ -168,7 +174,9 @@ class FileSystem : public SubsystemInterface
 		rts::string_key<AsciiString>, FileExistData,
 		rts::string_key_hash<AsciiString>,
 		rts::string_key_equal<AsciiString> > FileExistMap;
+
 	mutable FileExistMap m_fileExist;
+	mutable FastCriticalSectionClass m_fileExistMutex;
 #endif
 };
 
diff --git a/Core/GameEngine/Source/Common/System/FileSystem.cpp b/Core/GameEngine/Source/Common/System/FileSystem.cpp
index 8d5589b5f6..46d468d4a0 100644
--- a/Core/GameEngine/Source/Common/System/FileSystem.cpp
+++ b/Core/GameEngine/Source/Common/System/FileSystem.cpp
@@ -192,6 +192,7 @@ File*		FileSystem::openFile( const Char *filename, Int access, size_t bufferSize
 #if ENABLE_FILESYSTEM_EXISTENCE_CACHE
 			if (file != NULL && (file->getAccess() & File::CREATE))
 			{
+				FastCriticalSectionClass::LockClass lock(m_fileExistMutex);
 				FileExistMap::iterator it = m_fileExist.find(FileExistMap::key_type::temporary(filename));
 				if (it != m_fileExist.end())
 				{
@@ -227,6 +228,7 @@ Bool FileSystem::doesFileExist(const Char *filename, FileInstance instance) cons
 
 #if ENABLE_FILESYSTEM_EXISTENCE_CACHE
 	{
+		FastCriticalSectionClass::LockClass lock(m_fileExistMutex);
 		FileExistMap::const_iterator it = m_fileExist.find(FileExistMap::key_type::temporary(filename));
 		if (it != m_fileExist.end())
 		{
@@ -244,7 +246,10 @@ Bool FileSystem::doesFileExist(const Char *filename, FileInstance instance) cons
 		if (instance == 0)
 		{
 #if ENABLE_FILESYSTEM_EXISTENCE_CACHE
-			m_fileExist[filename];
+			{
+				FastCriticalSectionClass::LockClass lock(m_fileExistMutex);
+				m_fileExist[filename];
+			}
 #endif
 			return TRUE;
 		}
@@ -255,15 +260,21 @@ Bool FileSystem::doesFileExist(const Char *filename, FileInstance instance) cons
 	if (TheArchiveFileSystem->doesFileExist(filename, instance))
 	{
 #if ENABLE_FILESYSTEM_EXISTENCE_CACHE
-		FileExistMap::mapped_type& value = m_fileExist[filename];
-		value.instanceExists = max(value.instanceExists, instance);
+		{
+			FastCriticalSectionClass::LockClass lock(m_fileExistMutex);
+			FileExistMap::mapped_type& value = m_fileExist[filename];
+			value.instanceExists = max(value.instanceExists, instance);
+		}
 #endif
 		return TRUE;
 	}
 
 #if ENABLE_FILESYSTEM_EXISTENCE_CACHE
-	FileExistMap::mapped_type& value = m_fileExist[filename];
-	value.instanceDoesNotExist = min(value.instanceDoesNotExist, instance);
+	{
+		FastCriticalSectionClass::LockClass lock(m_fileExistMutex);
+		FileExistMap::mapped_type& value = m_fileExist[filename];
+		value.instanceDoesNotExist = min(value.instanceDoesNotExist, instance);
+	}
 #endif
 	return FALSE;
 }