https://github.com/kkos/oniguruma/issues/55
https://github.com/kkos/oniguruma/commit/f015fbdd95f76438cd86366467bb2b39870dd7c6
https://github.com/kkos/oniguruma/commit/b4bf968ad52afe14e60a2dc8a95d3555c543353a

Author: K.Kosako <kosako@sofnec.co.jp>

--- a/regparse.c
+++ b/regparse.c
@@ -3064,7 +3064,7 @@
 	PUNFETCH;
 	prev = p;
 	num = scan_unsigned_octal_number(&p, end, 3, enc);
-	if (num < 0) return ONIGERR_TOO_BIG_NUMBER;
+	if (num < 0 || num >= 256) return ONIGERR_TOO_BIG_NUMBER;
 	if (p == prev) {  /* can't read nothing. */
 	  num = 0; /* but, it's not error */
 	}
@@ -3436,7 +3436,7 @@
       if (IS_SYNTAX_OP(syn, ONIG_SYN_OP_ESC_OCTAL3)) {
 	prev = p;
 	num = scan_unsigned_octal_number(&p, end, (c == '0' ? 2:3), enc);
-	if (num < 0) return ONIGERR_TOO_BIG_NUMBER;
+	if (num < 0 || num >= 256) return ONIGERR_TOO_BIG_NUMBER;
 	if (p == prev) {  /* can't read nothing. */
 	  num = 0; /* but, it's not error */
 	}
@@ -4084,7 +4084,12 @@
   switch (*state) {
   case CCS_VALUE:
     if (*type == CCV_SB)
+    {
+      if (*vs > 0xff)
+          return ONIGERR_INVALID_CODE_POINT_VALUE;
+
       BITSET_SET_BIT(cc->bs, (int )(*vs));
+    }
     else if (*type == CCV_CODE_POINT) {
       r = add_code_range(&(cc->mbuf), env, *vs, *vs);
       if (r < 0) return r;