diff --git a/third_party/libtiff/0033-avail-out-overflow.patch b/third_party/libtiff/0033-avail-out-overflow.patch
new file mode 100644
index 0000000..08ea746
--- /dev/null
+++ b/third_party/libtiff/0033-avail-out-overflow.patch
@@ -0,0 +1,13 @@
+diff --git a/third_party/libtiff/tif_pixarlog.c b/third_party/libtiff/tif_pixarlog.c
+index 626409058..e72cc0be9 100644
+--- a/third_party/libtiff/tif_pixarlog.c
++++ b/third_party/libtiff/tif_pixarlog.c
+@@ -799,7 +799,7 @@ PixarLogDecode(TIFF* tif, uint8* op, tmsize_t occ, uint16 s)
+ 		return (0);
+ 	}
+ 	/* Check that we will not fill more than what was allocated */
+-	if ((tmsize_t)sp->stream.avail_out > sp->tbuf_size)
++        if (sp->tbuf_size < 0 || sp->stream.avail_out > (uInt) sp->tbuf_size)
+ 	{
+ 		TIFFErrorExt(tif->tif_clientdata, module, "sp->stream.avail_out > sp->tbuf_size");
+ 		return (0);
diff --git a/third_party/libtiff/README.pdfium b/third_party/libtiff/README.pdfium
index 4691827..b7d70e7 100644
--- a/third_party/libtiff/README.pdfium
+++ b/third_party/libtiff/README.pdfium
@@ -15,3 +15,4 @@
 0028-nstrips-OOM.patch: return error for excess number of tiles/strips.
 0031-safe_size_ingtStripContig.patch: return error if the size to read overflow from int32.
 0032-builtin-codecs.patch: make _TIFFBuiltinCODECS const data.
+0033-0033-avail-out-overflow.patch: signed comparison in PixarLogDecode().
\ No newline at end of file
diff --git a/third_party/libtiff/tif_pixarlog.c b/third_party/libtiff/tif_pixarlog.c
index 6264090..e72cc0b 100644
--- a/third_party/libtiff/tif_pixarlog.c
+++ b/third_party/libtiff/tif_pixarlog.c
@@ -799,7 +799,7 @@
 		return (0);
 	}
 	/* Check that we will not fill more than what was allocated */
-	if ((tmsize_t)sp->stream.avail_out > sp->tbuf_size)
+        if (sp->tbuf_size < 0 || sp->stream.avail_out > (uInt) sp->tbuf_size)
 	{
 		TIFFErrorExt(tif->tif_clientdata, module, "sp->stream.avail_out > sp->tbuf_size");
 		return (0);