diff --git a/Common/Data/Format/ZIMLoad.cpp b/Common/Data/Format/ZIMLoad.cpp
index daace4992d..0113a46d71 100644
--- a/Common/Data/Format/ZIMLoad.cpp
+++ b/Common/Data/Format/ZIMLoad.cpp
@@ -1,6 +1,7 @@
 #include <cstring>
 #include <cstdio>
 #include <cstdlib>
+#include <limits>
 #include <zstd.h>
 
 #include "zlib.h"
@@ -50,6 +51,10 @@ int ezuncompress(unsigned char* pDest, long* pnDestLen, const unsigned char* pSr
 }
 
 int LoadZIMPtr(const uint8_t *zim, size_t datasize, int *width, int *height, int *flags, uint8_t **image) {
+	if (datasize < 16) {
+		ERROR_LOG(Log::IO, "ZIM file is too small");
+		return 0;
+	}
 	if (zim[0] != 'Z' || zim[1] != 'I' || zim[2] != 'M' || zim[3] != 'G') {
 		ERROR_LOG(Log::IO, "Not a ZIM file");
 		return 0;
@@ -58,29 +63,53 @@ int LoadZIMPtr(const uint8_t *zim, size_t datasize, int *width, int *height, int
 	memcpy(height, zim + 8, 4);
 	memcpy(flags, zim + 12, 4);
 
+	if (*width <= 0 || *height <= 0) {
+		ERROR_LOG(Log::IO, "Invalid ZIM dimensions %i x %i", *width, *height);
+		return 0;
+	}
+
 	int num_levels = 1;
-	int image_data_size[ZIM_MAX_MIP_LEVELS]{};
+	size_t image_data_size[ZIM_MAX_MIP_LEVELS]{};
 	if (*flags & ZIM_HAS_MIPS) {
 		num_levels = log2i(*width < *height ? *width : *height) + 1;
 	}
-	int total_data_size = 0;
+	if (num_levels > ZIM_MAX_MIP_LEVELS) {
+		ERROR_LOG(Log::IO, "Too many ZIM mip levels: %i", num_levels);
+		return 0;
+	}
+
+	size_t total_data_size = 0;
 	for (int i = 0; i < num_levels; i++) {
 		if (i > 0) {
 			width[i] = width[i-1] / 2;
 			height[i] = height[i-1] / 2;
 		}
+
+		const size_t level_width = (size_t)width[i];
+		const size_t level_height = (size_t)height[i];
+		size_t bytes_per_pixel;
 		switch (*flags & ZIM_FORMAT_MASK) {
 		case ZIM_RGBA8888:
-			image_data_size[i] = width[i] * height[i] * 4; 
+			bytes_per_pixel = 4;
 			break;
 		case ZIM_RGBA4444:
 		case ZIM_RGB565:
-			image_data_size[i] = width[i] * height[i] * 2;
+			bytes_per_pixel = 2;
 			break;
 		default:
 			ERROR_LOG(Log::IO, "Invalid ZIM format %i", *flags & ZIM_FORMAT_MASK);
 			return 0;
 		}
+		if (level_width > std::numeric_limits<size_t>::max() / level_height ||
+			level_width * level_height > std::numeric_limits<size_t>::max() / bytes_per_pixel) {
+			ERROR_LOG(Log::IO, "ZIM image size is too large");
+			return 0;
+		}
+		image_data_size[i] = level_width * level_height * bytes_per_pixel;
+		if (total_data_size > std::numeric_limits<size_t>::max() - image_data_size[i]) {
+			ERROR_LOG(Log::IO, "ZIM mip data size is too large");
+			return 0;
+		}
 		total_data_size += image_data_size[i];
 	}
 
@@ -89,14 +118,29 @@ int LoadZIMPtr(const uint8_t *zim, size_t datasize, int *width, int *height, int
 		return 0;
 	}
 
+	const size_t payload_size = datasize - 16;
+	if (!(*flags & (ZIM_ZLIB_COMPRESSED | ZIM_ZSTD_COMPRESSED)) && payload_size != total_data_size) {
+		ERROR_LOG(Log::IO, "Wrong size data in ZIM: %i vs %i", (int)payload_size, (int)total_data_size);
+		return 0;
+	}
+	if ((*flags & ZIM_ZLIB_COMPRESSED) &&
+		(total_data_size > (size_t)std::numeric_limits<long>::max() || payload_size > (size_t)std::numeric_limits<long>::max())) {
+		ERROR_LOG(Log::IO, "ZIM zlib data is too large");
+		return 0;
+	}
+
 	image[0] = (uint8_t *)malloc(total_data_size);
+	if (!image[0]) {
+		ERROR_LOG(Log::IO, "Failed to allocate %lld bytes for ZIM image", (long long)total_data_size);
+		return 0;
+	}
 	for (int i = 1; i < num_levels; i++) {
 		image[i] = image[i-1] + image_data_size[i-1];
 	}
 
 	if (*flags & ZIM_ZLIB_COMPRESSED) {
 		long outlen = (long)total_data_size;
-		int retcode = ezuncompress(*image, &outlen, (unsigned char *)(zim + 16), (long)datasize - 16);
+		int retcode = ezuncompress(*image, &outlen, (unsigned char *)(zim + 16), (long)payload_size);
 		if (Z_OK != retcode) {
 			ERROR_LOG(Log::IO, "ZIM zlib format decompression failed: %d", retcode);
 			free(*image);
@@ -108,7 +152,7 @@ int LoadZIMPtr(const uint8_t *zim, size_t datasize, int *width, int *height, int
 			ERROR_LOG(Log::IO, "Wrong size data in ZIM: %i vs %i", (int)outlen, (int)total_data_size);
 		}
 	} else if (*flags & ZIM_ZSTD_COMPRESSED) {
-		size_t outlen = ZSTD_decompress(*image, total_data_size, zim + 16, datasize - 16);
+		size_t outlen = ZSTD_decompress(*image, total_data_size, zim + 16, payload_size);
 		if (outlen != (size_t)total_data_size) {
 			ERROR_LOG(Log::IO, "ZIM zstd format decompression failed: %lld", (long long)outlen);
 			free(*image);
@@ -116,10 +160,7 @@ int LoadZIMPtr(const uint8_t *zim, size_t datasize, int *width, int *height, int
 			return 0;
 		}
 	} else {
-		memcpy(*image, zim + 16, datasize - 16);
-		if (datasize - 16 != (size_t)total_data_size) {
-			ERROR_LOG(Log::IO, "Wrong size data in ZIM: %i vs %i", (int)(datasize-16), (int)total_data_size);
-		}
+		memcpy(*image, zim + 16, payload_size);
 	}
 	return num_levels;
 }