diff --git a/Core/FileSystems/ISOFileSystem.cpp b/Core/FileSystems/ISOFileSystem.cpp
index 20994af8b4..e3a6ad68b4 100644
--- a/Core/FileSystems/ISOFileSystem.cpp
+++ b/Core/FileSystems/ISOFileSystem.cpp
@@ -302,6 +302,20 @@ void ISOFileSystem::ReadDirectory(TreeEntry *root) const {
 				ERROR_LOG(Log::FileSystem, "File '%s' starts or ends outside ISO. firstDataSector: %d len: %d", entry->BuildPath().c_str(), (int)dir.firstDataSector, (int)dir.dataLength);
 			}
 
+			// The directory record is untrusted, and callers size host buffers from entry->size, so
+			// don't let it claim more data than the image actually contains. We clamp rather than
+			// drop the entry - truncated ISOs are common and used to work with just the warning
+			// above, and dropping EBOOT.BIN would turn that into an unbootable game. For a sane
+			// file this is a no-op, since the extent always fits in its sectors.
+			if (isFile) {
+				const u64 numBlocks = blockDevice->GetNumBlocks();
+				const u64 firstSector = dir.firstDataSector;
+				const s64 availableBytes = firstSector >= numBlocks ? 0 : (s64)((numBlocks - firstSector) * (u64)sectorSize);
+				if (entry->size > availableBytes) {
+					entry->size = availableBytes;
+				}
+			}
+
 			if (entry->isDirectory && !relative) {
 				if (entry->startsector == root->startsector) {
 					blockDevice->NotifyReadError();
@@ -485,7 +499,11 @@ int ISOFileSystem::Ioctl(u32 handle, u32 cmd, u32 indataPtr, u32 inlen, u32 outd
 		}
 
 		VolDescriptor desc;
-		blockDevice->ReadBlock(16, (u8 *)&desc);
+		if (!blockDevice->ReadBlock(16, (u8 *)&desc)) {
+			blockDevice->NotifyReadError();
+			ERROR_LOG(Log::FileSystem, "Failed to read volume descriptor for the path table");
+			return SCE_KERNEL_ERROR_ERRNO_IO_ERROR;
+		}
 		if (outlen < (u32)desc.pathTableLength) {
 			return SCE_KERNEL_ERROR_ERRNO_INVALID_ARGUMENT;
 		} else {
@@ -503,7 +521,9 @@ int ISOFileSystem::Ioctl(u32 handle, u32 cmd, u32 indataPtr, u32 inlen, u32 outd
 				u8 temp[2048];
 				// `blocks` whole sectors starting at `block` were already consumed by
 				// ReadBlocks() above, so the trailing partial sector is the next one.
-				blockDevice->ReadBlock(block + blocks, temp);
+				if (!blockDevice->ReadBlock(block + blocks, temp)) {
+					memset(temp, 0, sizeof(temp));
+				}
 				memcpy(out, temp, size);
 			}
 			return 0;
@@ -602,7 +622,11 @@ size_t ISOFileSystem::ReadFile(u32 handle, u8 *pointer, s64 size, int &usec) {
 
 		const u8 *const start = pointer;
 		if (firstBlockSize > 0) {
-			blockDevice->ReadBlock(secNum++, theSector);
+			// theSector is uninitialized stack memory, so on a failed read we must not copy it out -
+			// that would hand host stack contents to the game.
+			if (!blockDevice->ReadBlock(secNum++, theSector)) {
+				memset(theSector, 0, sizeof(theSector));
+			}
 			memcpy(pointer, theSector + firstBlockOffset, firstBlockSize);
 			pointer += firstBlockSize;
 		}
@@ -613,7 +637,9 @@ size_t ISOFileSystem::ReadFile(u32 handle, u8 *pointer, s64 size, int &usec) {
 			pointer += middleSize;
 		}
 		if (lastBlockSize > 0) {
-			blockDevice->ReadBlock(secNum++, theSector);
+			if (!blockDevice->ReadBlock(secNum++, theSector)) {
+				memset(theSector, 0, sizeof(theSector));
+			}
 			memcpy(pointer, theSector, lastBlockSize);
 			pointer += lastBlockSize;
 		}
diff --git a/Core/Util/GameManager.cpp b/Core/Util/GameManager.cpp
index 8387168892..ba4eb5be27 100644
--- a/Core/Util/GameManager.cpp
+++ b/Core/Util/GameManager.cpp
@@ -549,6 +549,7 @@ std::string GameManager::GetPBPGameID(FileLoader *loader) const {
 }
 
 std::string GameManager::GetISOGameID(FileLoader *loader) const {
+	static constexpr s64 MAX_PARAM_SFO_SIZE = 1024 * 1024;
 	SequentialHandleAllocator handles;
 	std::string errorString;
 	std::shared_ptr<BlockDevice> bd(ConstructBlockDevice(loader, &errorString));
@@ -566,10 +567,16 @@ std::string GameManager::GetISOGameID(FileLoader *loader) const {
 	if (handle < 0) {
 		return "";
 	}
+	if (info.size < 0 || info.size > MAX_PARAM_SFO_SIZE) {
+		WARN_LOG(Log::Loader, "Ignoring implausibly large PARAM.SFO (%lld bytes)", (long long)info.size);
+		umd.CloseFile(handle);
+		return "";
+	}
 
 	std::string sfoData;
-	sfoData.resize(info.size);
-	umd.ReadFile(handle, (u8 *)&sfoData[0], info.size);
+	sfoData.resize((size_t)info.size);
+	if (info.size > 0)
+		umd.ReadFile(handle, (u8 *)sfoData.data(), info.size);
 	umd.CloseFile(handle);
 
 	ParamSFOData sfo;
diff --git a/UI/GameInfoCache.cpp b/UI/GameInfoCache.cpp
index 881f8d550e..35a9662e35 100644
--- a/UI/GameInfoCache.cpp
+++ b/UI/GameInfoCache.cpp
@@ -450,11 +450,16 @@ void GameInfo::SetupTexture(Draw::DrawContext *thin3d, GameInfoTex &tex, int max
 
 // Will clear contents on failure.
 static bool ReadFileToString(IFileSystem *fs, std::string_view filename, std::string *contents, std::mutex *mtx) {
+	static constexpr s64 MAX_GAME_INFO_FILE_SIZE = 64 * 1024 * 1024;
 	std::string fn(filename);
 	PSPFileInfo info = fs->GetFileInfo(fn);
 	if (!info.exists) {
 		return false;
 	}
+	if (info.size < 0 || info.size > MAX_GAME_INFO_FILE_SIZE) {
+		WARN_LOG(Log::UI, "Ignoring implausibly large game metadata file %s (%lld bytes)", fn.c_str(), (long long)info.size);
+		return false;
+	}
 
 	int handle = fs->OpenFile(fn, FILEACCESS_READ);
 	if (handle < 0) {