diff -up php-5.2.17/ext/exif/exif.c.CVE-2011-4566 php-5.2.17/ext/exif/exif.c
--- php-5.2.17/ext/exif/exif.c.CVE-2011-4566	2012-01-11 15:00:23.000000000 +0700
+++ php-5.2.17/ext/exif/exif.c	2012-01-11 15:02:25.000000000 +0700
@@ -2873,11 +2873,11 @@ static int exif_process_IFD_TAG(image_in
 		offset_val = php_ifd_get32u(dir_entry+8, ImageInfo->motorola_intel);
 		/* If its bigger than 4 bytes, the dir entry contains an offset. */
 		value_ptr = offset_base+offset_val;
-		if (offset_val+byte_count > IFDlength || value_ptr < dir_entry) {
+		if (byte_count > IFDlength || offset_val > IFDlength-byte_count || value_ptr < dir_entry) {
 			/* It is important to check for IMAGE_FILETYPE_TIFF
 			 * JPEG does not use absolute pointers instead its pointers are
 			 * relative to the start of the TIFF header in APP1 section. */
-			if (offset_val+byte_count>ImageInfo->FileSize || (ImageInfo->FileType!=IMAGE_FILETYPE_TIFF_II && ImageInfo->FileType!=IMAGE_FILETYPE_TIFF_MM && ImageInfo->FileType!=IMAGE_FILETYPE_JPEG)) {
+			if (byte_count > ImageInfo->FileSize || offset_val>ImageInfo->FileSize-byte_count || (ImageInfo->FileType!=IMAGE_FILETYPE_TIFF_II && ImageInfo->FileType!=IMAGE_FILETYPE_TIFF_MM && ImageInfo->FileType!=IMAGE_FILETYPE_JPEG)) {
 				if (value_ptr < dir_entry) {
 					/* we can read this if offset_val > 0 */
 					/* some files have their values in other parts of the file */