diff --git a/third_party/libtiff/tif_dir.c b/third_party/libtiff/tif_dir.c
index 81b849374..72148411f 100644
--- a/third_party/libtiff/tif_dir.c
+++ b/third_party/libtiff/tif_dir.c
@@ -31,6 +31,7 @@
  * (and also some miscellaneous stuff)
  */
 #include "tiffiop.h"
+#include <float.h>
 
 /*
  * These are used in the backwards compatibility code...
@@ -154,6 +155,15 @@ bad:
        return (0);
 }
 
+static float TIFFClampDoubleToFloat( double val )
+{
+    if( val > FLT_MAX )
+        return FLT_MAX;
+    if( val < -FLT_MAX )
+        return -FLT_MAX;
+    return (float)val;
+}
+
 static int
 _TIFFVSetField(TIFF* tif, uint32 tag, va_list ap)
 {
@@ -312,13 +322,13 @@ _TIFFVSetField(TIFF* tif, uint32 tag, va_list ap)
         dblval = va_arg(ap, double);
         if( dblval < 0 )
             goto badvaluedouble;
-               td->td_xresolution = (float) dblval;
+               td->td_xresolution = TIFFClampDoubleToFloat( dblval );
                break;
        case TIFFTAG_YRESOLUTION:
         dblval = va_arg(ap, double);
         if( dblval < 0 )
             goto badvaluedouble;
-               td->td_yresolution = (float) dblval;
+               td->td_yresolution = TIFFClampDoubleToFloat( dblval );
                break;
        case TIFFTAG_PLANARCONFIG:
                v = (uint16) va_arg(ap, uint16_vap);
@@ -327,10 +337,10 @@ _TIFFVSetField(TIFF* tif, uint32 tag, va_list ap)
                td->td_planarconfig = (uint16) v;
                break;
        case TIFFTAG_XPOSITION:
-               td->td_xposition = (float) va_arg(ap, double);
+               td->td_xposition = TIFFClampDoubleToFloat( va_arg(ap, double) );
                break;
        case TIFFTAG_YPOSITION:
-               td->td_yposition = (float) va_arg(ap, double);
+               td->td_yposition = TIFFClampDoubleToFloat( va_arg(ap, double) );
                break;
        case TIFFTAG_RESOLUTIONUNIT:
                v = (uint16) va_arg(ap, uint16_vap);
diff --git a/third_party/libtiff/tif_dirread.c b/third_party/libtiff/tif_dirread.c
index 7dbcf6d86..0926e1625 100644
--- a/third_party/libtiff/tif_dirread.c
+++ b/third_party/libtiff/tif_dirread.c
@@ -40,6 +40,7 @@
  */
 
 #include "tiffiop.h"
+#include <float.h>
 
 #define IGNORE 0          /* tag placeholder used below */
 #define FAILED_FII    ((uint32) -1)
@@ -2405,7 +2406,14 @@ static enum TIFFReadDirEntryErr TIFFReadDirEntryFloatArray(TIFF* tif, TIFFDirEnt
                                ma=(double*)origdata;
                                mb=data;
                                for (n=0; n<count; n++)
-                                       *mb++=(float)(*ma++);
+                               {
+                                       double val = *ma++;
+                                       if( val > FLT_MAX )
+                                               val = FLT_MAX;
+                                       else if( val < -FLT_MAX )
+                                               val = -FLT_MAX;
+                                       *mb++=(float)val;
+                               }
                        }
                        break;
        }
@@ -2871,7 +2879,10 @@ static enum TIFFReadDirEntryErr TIFFReadDirEntryCheckedRational(TIFF* tif, TIFFD
                m.l = direntry->tdir_offset.toff_long8;
        if (tif->tif_flags&TIFF_SWAB)
                TIFFSwabArrayOfLong(m.i,2);
-       if (m.i[0]==0)
+       /* Not completely sure what we should do when m.i[1]==0, but some */
+       /* sanitizers do not like division by 0.0: */
+       /* http://bugzilla.maptools.org/show_bug.cgi?id=2644 */
+       if (m.i[0]==0 || m.i[1]==0)
                *value=0.0;
        else
                *value=(double)m.i[0]/(double)m.i[1];
@@ -2899,7 +2910,10 @@ static enum TIFFReadDirEntryErr TIFFReadDirEntryCheckedSrational(TIFF* tif, TIFF
                m.l=direntry->tdir_offset.toff_long8;
        if (tif->tif_flags&TIFF_SWAB)
                TIFFSwabArrayOfLong(m.i,2);
-       if ((int32)m.i[0]==0)
+       /* Not completely sure what we should do when m.i[1]==0, but some */
+       /* sanitizers do not like division by 0.0: */
+       /* http://bugzilla.maptools.org/show_bug.cgi?id=2644 */
+       if ((int32)m.i[0]==0 || m.i[1]==0)
                *value=0.0;
        else
                *value=(double)((int32)m.i[0])/(double)m.i[1];
diff --git a/third_party/libtiff/tif_dirwrite.c b/third_party/libtiff/tif_dirwrite.c
index d34f6f611..f4d8034ec 100644
--- a/third_party/libtiff/tif_dirwrite.c
+++ b/third_party/libtiff/tif_dirwrite.c
@@ -30,6 +30,7 @@
  * Directory Write Support Routines.
  */
 #include "tiffiop.h"
+#include <float.h>
 
 #ifdef HAVE_IEEEFP
 #define TIFFCvtNativeToIEEEFloat(tif, n, fp)
@@ -939,6 +940,69 @@ bad:
        return(0);
 }
 
+static float TIFFClampDoubleToFloat( double val )
+{
+    if( val > FLT_MAX )
+        return FLT_MAX;
+    if( val < -FLT_MAX )
+        return -FLT_MAX;
+    return (float)val;
+}
+
+static int8 TIFFClampDoubleToInt8( double val )
+{
+    if( val > 127 )
+        return 127;
+    if( val < -128 || val != val )
+        return -128;
+    return (int8)val;
+}
+
+static int16 TIFFClampDoubleToInt16( double val )
+{
+    if( val > 32767 )
+        return 32767;
+    if( val < -32768 || val != val )
+        return -32768;
+    return (int16)val;
+}
+
+static int32 TIFFClampDoubleToInt32( double val )
+{
+    if( val > 0x7FFFFFFF )
+        return 0x7FFFFFFF;
+    if( val < -0x7FFFFFFF-1 || val != val )
+        return -0x7FFFFFFF-1;
+    return (int32)val;
+}
+
+static uint8 TIFFClampDoubleToUInt8( double val )
+{
+    if( val < 0 )
+        return 0;
+    if( val > 255 || val != val )
+        return 255;
+    return (uint8)val;
+}
+
+static uint16 TIFFClampDoubleToUInt16( double val )
+{
+    if( val < 0 )
+        return 0;
+    if( val > 65535 || val != val )
+        return 65535;
+    return (uint16)val;
+}
+
+static uint32 TIFFClampDoubleToUInt32( double val )
+{
+    if( val < 0 )
+        return 0;
+    if( val > 0xFFFFFFFFU || val != val )
+        return 0xFFFFFFFFU;
+    return (uint32)val;
+}
+
 static int
 TIFFWriteDirectoryTagSampleformatArray(TIFF* tif, uint32* ndir, TIFFDirEntry* dir, uint16 tag, uint32 count, double* value)
 {
@@ -959,7 +1023,7 @@ TIFFWriteDirectoryTagSampleformatArray(TIFF* tif, uint32* ndir, TIFFDirEntry* di
                        if (tif->tif_dir.td_bitspersample<=32)
                        {
                                for (i = 0; i < count; ++i)
-                                       ((float*)conv)[i] = (float)value[i];
+                                       ((float*)conv)[i] = TIFFClampDoubleToFloat(value[i]);
                                ok = TIFFWriteDirectoryTagFloatArray(tif,ndir,dir,tag,count,(float*)conv);
                        }
                        else
@@ -971,19 +1035,19 @@ TIFFWriteDirectoryTagSampleformatArray(TIFF* tif, uint32* ndir, TIFFDirEntry* di
                        if (tif->tif_dir.td_bitspersample<=8)
                        {
                                for (i = 0; i < count; ++i)
-                                       ((int8*)conv)[i] = (int8)value[i];
+                                       ((int8*)conv)[i] = TIFFClampDoubleToInt8(value[i]);
                                ok = TIFFWriteDirectoryTagSbyteArray(tif,ndir,dir,tag,count,(int8*)conv);
                        }
                        else if (tif->tif_dir.td_bitspersample<=16)
                        {
                                for (i = 0; i < count; ++i)
-                                       ((int16*)conv)[i] = (int16)value[i];
+                                       ((int16*)conv)[i] = TIFFClampDoubleToInt16(value[i]);
                                ok = TIFFWriteDirectoryTagSshortArray(tif,ndir,dir,tag,count,(int16*)conv);
                        }
                        else
                        {
                                for (i = 0; i < count; ++i)
-                                       ((int32*)conv)[i] = (int32)value[i];
+                                       ((int32*)conv)[i] = TIFFClampDoubleToInt32(value[i]);
                                ok = TIFFWriteDirectoryTagSlongArray(tif,ndir,dir,tag,count,(int32*)conv);
                        }
                        break;
@@ -991,19 +1055,19 @@ TIFFWriteDirectoryTagSampleformatArray(TIFF* tif, uint32* ndir, TIFFDirEntry* di
                        if (tif->tif_dir.td_bitspersample<=8)
                        {
                                for (i = 0; i < count; ++i)
-                                       ((uint8*)conv)[i] = (uint8)value[i];
+                                       ((uint8*)conv)[i] = TIFFClampDoubleToUInt8(value[i]);
                                ok = TIFFWriteDirectoryTagByteArray(tif,ndir,dir,tag,count,(uint8*)conv);
                        }
                        else if (tif->tif_dir.td_bitspersample<=16)
                        {
                                for (i = 0; i < count; ++i)
-                                       ((uint16*)conv)[i] = (uint16)value[i];
+                                       ((uint16*)conv)[i] = TIFFClampDoubleToUInt16(value[i]);
                                ok = TIFFWriteDirectoryTagShortArray(tif,ndir,dir,tag,count,(uint16*)conv);
                        }
                        else
                        {
                                for (i = 0; i < count; ++i)
-                                       ((uint32*)conv)[i] = (uint32)value[i];
+                                       ((uint32*)conv)[i] = TIFFClampDoubleToUInt32(value[i]);
                                ok = TIFFWriteDirectoryTagLongArray(tif,ndir,dir,tag,count,(uint32*)conv);
                        }
                        break;
@@ -2094,15 +2158,25 @@ TIFFWriteDirectoryTagCheckedSlong8Array(TIFF* tif, uint32* ndir, TIFFDirEntry* d
 static int
 TIFFWriteDirectoryTagCheckedRational(TIFF* tif, uint32* ndir, TIFFDirEntry* dir, uint16 tag, double value)
 {
+       static const char module[] = "TIFFWriteDirectoryTagCheckedRational";
        uint32 m[2];
-       assert(value>=0.0);
        assert(sizeof(uint32)==4);
-       if (value<=0.0)
+       if( value < 0 )
+       {
+               TIFFErrorExt(tif->tif_clientdata,module,"Negative value is illegal");
+               return 0;
+       }
+       else if( value != value )
+       {
+               TIFFErrorExt(tif->tif_clientdata,module,"Not-a-number value is illegal");
+               return 0;
+       }
+       else if (value==0.0)
        {
                m[0]=0;
                m[1]=1;
        }
-       else if (value==(double)(uint32)value)
+       else if (value <= 0xFFFFFFFFU && value==(double)(uint32)value)
        {
                m[0]=(uint32)value;
                m[1]=1;
@@ -2143,12 +2217,13 @@ TIFFWriteDirectoryTagCheckedRationalArray(TIFF* tif, uint32* ndir, TIFFDirEntry*
        }
        for (na=value, nb=m, nc=0; nc<count; na++, nb+=2, nc++)
        {
-               if (*na<=0.0)
+               if (*na<=0.0 || *na != *na)
                {
                        nb[0]=0;
                        nb[1]=1;
                }
-               else if (*na==(float)(uint32)(*na))
+               else if (*na >= 0 && *na <= (float)0xFFFFFFFFU &&
+                                       *na==(float)(uint32)(*na))
                {
                        nb[0]=(uint32)(*na);
                        nb[1]=1;
diff --git a/third_party/libtiff/tif_jpeg.c b/third_party/libtiff/tif_jpeg.c
index abd0b0aa2..4f154a7c2 100644
--- a/third_party/libtiff/tif_jpeg.c
+++ b/third_party/libtiff/tif_jpeg.c
@@ -1634,6 +1634,20 @@ JPEGSetupEncode(TIFF* tif)
        case PHOTOMETRIC_YCBCR:
                sp->h_sampling = td->td_ycbcrsubsampling[0];
                sp->v_sampling = td->td_ycbcrsubsampling[1];
+               if( sp->h_sampling == 0 || sp->v_sampling == 0 )
+               {
+                       TIFFErrorExt(tif->tif_clientdata, module,
+                                       "Invalig horizontal/vertical sampling value");
+                       return (0);
+               }
+               if( td->td_bitspersample > 16 )
+               {
+                       TIFFErrorExt(tif->tif_clientdata, module,
+                                                       "BitsPerSample %d not allowed for JPEG",
+                                                       td->td_bitspersample);
+                       return (0);
+               }
+
                /*
                 * A ReferenceBlackWhite field *must* be present since the
                 * default value is inappropriate for YCbCr.  Fill in the
diff --git a/third_party/libtiff/tif_read.c b/third_party/libtiff/tif_read.c
index 47686a473..c916ac8ac 100644
--- a/third_party/libtiff/tif_read.c
+++ b/third_party/libtiff/tif_read.c
@@ -420,16 +420,25 @@ TIFFReadRawStrip1(TIFF* tif, uint32 strip, void* buf, tmsize_t size,
                        return ((tmsize_t)(-1));
                }
        } else {
-               tmsize_t ma,mb;
+               tmsize_t ma;
                tmsize_t n;
-               ma=(tmsize_t)td->td_stripoffset[strip];
-               mb=ma+size;
-               if ((td->td_stripoffset[strip] > (uint64)TIFF_TMSIZE_T_MAX)||(ma>tif->tif_size))
+               if ((td->td_stripoffset[strip] > (uint64)TIFF_TMSIZE_T_MAX)||
+                               ((ma=(tmsize_t)td->td_stripoffset[strip])>tif->tif_size))
+               {
                        n=0;
-               else if ((mb<ma)||(mb<size)||(mb>tif->tif_size))
-                       n=tif->tif_size-ma;
+               }
+               else if( ma > TIFF_TMSIZE_T_MAX - size )
+               {
+                       n=0;
+               }
                else
-                       n=size;
+               {
+                       tmsize_t mb=ma+size;
+                       if (mb>tif->tif_size)
+                               n=tif->tif_size-ma;
+                       else
+                               n=size;
+               }
                if (n!=size) {
 #if defined(__WIN32__) && (defined(_MSC_VER) || defined(__MINGW32__))
                        TIFFErrorExt(tif->tif_clientdata, module,