diff --git a/mysql-test/r/ctype_utf32_uca.result b/mysql-test/r/ctype_utf32_uca.result
index fd5a4199217..a9f056b2e44 100644
--- a/mysql-test/r/ctype_utf32_uca.result
+++ b/mysql-test/r/ctype_utf32_uca.result
@@ -2415,5 +2415,25 @@ HEX(s1)
 00000061
 DROP TABLE t1;
 #
+# Bug #12319710 : INVALID MEMORY READ AND/OR CRASH IN 
+#   MY_UCA_CHARCMP WITH UTF32
+#
+SET collation_connection=utf32_unicode_ci;
+CREATE TABLE t1 (a TEXT CHARACTER SET utf32 COLLATE utf32_turkish_ci NOT NULL);
+INSERT INTO t1 VALUES ('a'), ('b');
+CREATE TABLE t2 (b VARBINARY(5) NOT NULL);
+#insert chars outside of BMP
+INSERT INTO t2 VALUEs (0x082837),(0x082837);
+#test for read-out-of-bounds with non-BMP chars as a LIKE pattern
+SELECT * FROM t1,t2 WHERE a LIKE b;
+a	b
+#test the original statement
+SELECT 1 FROM t1 AS t1_0 NATURAL LEFT OUTER JOIN t2 AS t2_0
+RIGHT JOIN t1 AS t1_1 ON t1_0.a LIKE t2_0.b;
+1
+1
+1
+DROP TABLE t1,t2;
+#
 # End of 5.5 tests
 #
diff --git a/mysql-test/t/ctype_utf32_uca.test b/mysql-test/t/ctype_utf32_uca.test
index a62ffbf95c7..1d79fbe1616 100644
--- a/mysql-test/t/ctype_utf32_uca.test
+++ b/mysql-test/t/ctype_utf32_uca.test
@@ -293,6 +293,27 @@ SET collation_connection=utf32_czech_ci;
 --source include/ctype_czech.inc
 --source include/ctype_like_ignorable.inc
 
+--echo #
+--echo # Bug #12319710 : INVALID MEMORY READ AND/OR CRASH IN 
+--echo #   MY_UCA_CHARCMP WITH UTF32
+--echo #
+
+SET collation_connection=utf32_unicode_ci;
+CREATE TABLE t1 (a TEXT CHARACTER SET utf32 COLLATE utf32_turkish_ci NOT NULL);
+INSERT INTO t1 VALUES ('a'), ('b');
+CREATE TABLE t2 (b VARBINARY(5) NOT NULL);
+
+--echo #insert chars outside of BMP
+INSERT INTO t2 VALUEs (0x082837),(0x082837);
+
+--echo #test for read-out-of-bounds with non-BMP chars as a LIKE pattern
+SELECT * FROM t1,t2 WHERE a LIKE b;
+
+--echo #test the original statement
+SELECT 1 FROM t1 AS t1_0 NATURAL LEFT OUTER JOIN t2 AS t2_0
+RIGHT JOIN t1 AS t1_1 ON t1_0.a LIKE t2_0.b;
+
+DROP TABLE t1,t2;
 
 --echo #
 --echo # End of 5.5 tests
diff --git a/strings/ctype-uca.c b/strings/ctype-uca.c
index d6be395535c..70d2df3bab9 100644
--- a/strings/ctype-uca.c
+++ b/strings/ctype-uca.c
@@ -42,6 +42,7 @@
 #define MY_UCA_NCHARS 256
 #define MY_UCA_CMASK  255
 #define MY_UCA_PSHIFT 8
+#define MAX_UCA_CHAR_WITH_EXPLICIT_WEIGHT 0xFFFF
 
 uint16 page000data[]= { /* 0000 (4 weights per char) */
 0x0000,0x0000,0x0000,0x0000, 0x0000,0x0000,0x0000,0x0000,
@@ -6984,7 +6985,7 @@ static int my_uca_scanner_next_any(my_uca_scanner *scanner)
       return -1;
     
     scanner->sbeg+= mb_len;
-    if (wc > 0xFFFF)
+    if (wc > MAX_UCA_CHAR_WITH_EXPLICIT_WEIGHT)
     {
       /* Return 0xFFFD as weight for all characters outside BMP */
       scanner->wbeg= nochar;
@@ -7322,6 +7323,33 @@ static size_t my_strnxfrm_uca(CHARSET_INFO *cs,
 
 
 
+/**
+  Helper function:
+  Find address of weights of the given character.
+  
+  @param weights  UCA weight array
+  @param lengths  UCA length array
+  @param ch       character Unicode code point
+  
+  @return Weight array
+    @retval  pointer to weight array for the given character,
+             or NULL if this page does not have implicit weights.
+*/
+
+static inline uint16 *
+my_char_weight_addr(CHARSET_INFO *cs, uint wc)
+{
+  uint page, ofst;
+  uchar *ucal= cs->sort_order;
+  uint16 **ucaw= cs->sort_order_big;
+
+  return wc > MAX_UCA_CHAR_WITH_EXPLICIT_WEIGHT ? NULL :
+         (ucaw[page= (wc >> 8)] ?
+          ucaw[page] + (ofst= (wc & 0xFF)) * ucal[page] :
+          NULL);
+}
+
+
 /*
   This function compares if two characters are the same.
   The sign +1 or -1 does not matter. The only
@@ -7332,17 +7360,20 @@ static size_t my_strnxfrm_uca(CHARSET_INFO *cs,
 
 static int my_uca_charcmp(CHARSET_INFO *cs, my_wc_t wc1, my_wc_t wc2)
 {
-  size_t page1= wc1 >> MY_UCA_PSHIFT;
-  size_t page2= wc2 >> MY_UCA_PSHIFT;
-  uchar *ucal= cs->sort_order;
-  uint16 **ucaw= cs->sort_order_big;
-  size_t length1= ucal[page1];
-  size_t length2= ucal[page2];
-  uint16 *weight1= ucaw[page1] + (wc1 & MY_UCA_CMASK) * ucal[page1];
-  uint16 *weight2= ucaw[page2] + (wc2 & MY_UCA_CMASK) * ucal[page2];
+  size_t length1, length2;
+  uint16 *weight1= my_char_weight_addr(cs, wc1);
+  uint16 *weight2= my_char_weight_addr(cs, wc2);
   
   if (!weight1 || !weight2)
     return wc1 != wc2;
+
+  /* Quickly compare first weights */
+  if (weight1[0] != weight2[0])
+    return 1;
+
+  /* Thoroughly compare all weights */
+  length1= cs->sort_order[wc1 >> MY_UCA_PSHIFT];
+  length2= cs->sort_order[wc2 >> MY_UCA_PSHIFT];
   
   if (length1 > length2)
     return memcmp((const void*)weight1, (const void*)weight2, length2*2) ?
@@ -7924,6 +7955,11 @@ static my_bool create_tailoring(CHARSET_INFO *cs, void *(*alloc)(size_t))
   */
   for (i=0; i < rc; i++)
   {
+    /* check if the shift or the reset characters are out of range */
+    if (rule[i].curr[0] > MAX_UCA_CHAR_WITH_EXPLICIT_WEIGHT ||
+        rule[i].base > MAX_UCA_CHAR_WITH_EXPLICIT_WEIGHT)
+      return 1;
+
     if (!rule[i].curr[1]) /* If not a contraction */
     {
       uint pageb= (rule[i].base >> 8) & 0xFF;