diff --git a/third_party/libtiff/tif_getimage.c b/third_party/libtiff/tif_getimage.c
index 23cb40951..2153f1348 100644
--- a/third_party/libtiff/tif_getimage.c
+++ b/third_party/libtiff/tif_getimage.c
@@ -962,6 +962,9 @@ gtStripContig(TIFFRGBAImage* img, uint32* raster, uint32 w, uint32 h)
 	int ret = 1, flip;
         tmsize_t maxstripsize;
 
+	if ((tmsize_t)img->row_offset > TIFF_SSIZE_T_MAX || (size_t)h > (size_t)TIFF_SSIZE_T_MAX)
+		return (0);
+
 	TIFFGetFieldDefaulted(tif, TIFFTAG_YCBCRSUBSAMPLING, &subsamplinghor, &subsamplingver);
 	if( subsamplingver == 0 ) {
 		TIFFErrorExt(tif->tif_clientdata, TIFFFileName(tif), "Invalid vertical YCbCr subsampling");
@@ -985,16 +988,34 @@ gtStripContig(TIFFRGBAImage* img, uint32* raster, uint32 w, uint32 h)
 	fromskew = (w < imagewidth ? imagewidth - w : 0);
 	for (row = 0; row < h; row += nrow)
 	{
+		tmsize_t actual_row;
 		rowstoread = rowsperstrip - (row + img->row_offset) % rowsperstrip;
 		nrow = (row + rowstoread > h ? h - row : rowstoread);
 		nrowsub = nrow;
 		if ((nrowsub%subsamplingver)!=0)
 			nrowsub+=subsamplingver-nrowsub%subsamplingver;
+
+		if (row > (size_t)TIFF_SSIZE_T_MAX - img->row_offset) {
+			ret = 0;
+			break;
+		}
+		actual_row = row + img->row_offset;
+		actual_row %= rowsperstrip;
+		if ((size_t)nrowsub > (size_t)TIFF_SSIZE_T_MAX || (size_t)actual_row > (size_t)TIFF_SSIZE_T_MAX - nrowsub) {
+			ret = 0;
+			break;
+		}
+		actual_row += nrowsub;
+		if ((tmsize_t)actual_row > TIFF_SSIZE_T_MAX / scanline) {
+			ret = 0;
+			break;
+		}
+
 		if (_TIFFReadEncodedStripAndAllocBuffer(tif,
 		    TIFFComputeStrip(tif,row+img->row_offset, 0),
 		    (void**)(&buf),
                     maxstripsize,
-		    ((row + img->row_offset)%rowsperstrip + nrowsub) * scanline)==(tmsize_t)(-1)
+		    actual_row * scanline)==(tmsize_t)(-1)
 		    && (buf == NULL || img->stoponerr))
 		{
 			ret = 0;
diff --git a/third_party/libtiff/tif_read.c b/third_party/libtiff/tif_read.c
index e63810cc7..dd3002669 100644
--- a/third_party/libtiff/tif_read.c
+++ b/third_party/libtiff/tif_read.c
@@ -558,6 +558,8 @@ _TIFFReadEncodedStripAndAllocBuffer(TIFF* tif, uint32 strip,
                                     void **buf, tmsize_t bufsizetoalloc,
                                     tmsize_t size_to_read)
 {
+    assert(size_to_read > 0);
+
     tmsize_t this_stripsize;
     uint16 plane;
 
diff --git a/third_party/libtiff/tiffconf.h b/third_party/libtiff/tiffconf.h
index 6292cc5cd..f57f6f709 100644
--- a/third_party/libtiff/tiffconf.h
+++ b/third_party/libtiff/tiffconf.h
@@ -132,13 +132,16 @@
 
 #if defined(_WIN64)
 #define TIFF_SSIZE_T signed __int64
+#define TIFF_SSIZE_T_MAX INT64_MAX
 #else
 #define TIFF_SSIZE_T signed int
+#define TIFF_SSIZE_T_MAX INT_MAX
 #endif
 
 #else
 
 #define TIFF_SSIZE_T signed long
+#define TIFF_SSIZE_T_MAX LONG_MAX
 
 #endif