diff --git a/NEWS.md b/NEWS.md
index 4939962a4049c9..f847fe6817821d 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -188,7 +188,7 @@ The following default gems are updated.
 * io-console 0.8.1
 * io-nonblock 0.3.2
 * io-wait 0.3.2
-* json 2.15.1
+* json 2.15.2
 * openssl 4.0.0.pre
 * optparse 0.7.0.dev.2
 * pp 0.6.3
diff --git a/ext/json/generator/generator.c b/ext/json/generator/generator.c
index 6a38cc60a7964f..f3f27b29d58ecd 100644
--- a/ext/json/generator/generator.c
+++ b/ext/json/generator/generator.c
@@ -1124,7 +1124,7 @@ static inline long increase_depth(struct generate_json_data *data)
     JSON_Generator_State *state = data->state;
     long depth = ++state->depth;
     if (RB_UNLIKELY(depth > state->max_nesting && state->max_nesting)) {
-        rb_raise(eNestingError, "nesting of %ld is too deep", --state->depth);
+        rb_raise(eNestingError, "nesting of %ld is too deep. Did you try to serialize objects with circular references?", --state->depth);
     }
     return depth;
 }
@@ -1491,10 +1491,39 @@ static VALUE cState_generate(int argc, VALUE *argv, VALUE self)
     rb_check_arity(argc, 1, 2);
     VALUE obj = argv[0];
     VALUE io = argc > 1 ? argv[1] : Qnil;
-    VALUE result = cState_partial_generate(self, obj, generate_json, io);
+    return cState_partial_generate(self, obj, generate_json, io);
+}
+
+static VALUE cState_generate_new(int argc, VALUE *argv, VALUE self)
+{
+    rb_check_arity(argc, 1, 2);
+    VALUE obj = argv[0];
+    VALUE io = argc > 1 ? argv[1] : Qnil;
+
     GET_STATE(self);
-    (void)state;
-    return result;
+
+    JSON_Generator_State new_state;
+    MEMCPY(&new_state, state, JSON_Generator_State, 1);
+
+    // FIXME: depth shouldn't be part of JSON_Generator_State, as that prevents it from being used concurrently.
+    new_state.depth = 0;
+
+    char stack_buffer[FBUFFER_STACK_SIZE];
+    FBuffer buffer = {
+        .io = RTEST(io) ? io : Qfalse,
+    };
+    fbuffer_stack_init(&buffer, state->buffer_initial_length, stack_buffer, FBUFFER_STACK_SIZE);
+
+    struct generate_json_data data = {
+        .buffer = &buffer,
+        .vstate = Qfalse,
+        .state = &new_state,
+        .obj = obj,
+        .func = generate_json
+    };
+    rb_rescue(generate_json_try, (VALUE)&data, generate_json_rescue, (VALUE)&data);
+
+    return fbuffer_finalize(&buffer);
 }
 
 static VALUE cState_initialize(int argc, VALUE *argv, VALUE self)
@@ -2072,7 +2101,7 @@ void Init_generator(void)
     rb_define_method(cState, "buffer_initial_length", cState_buffer_initial_length, 0);
     rb_define_method(cState, "buffer_initial_length=", cState_buffer_initial_length_set, 1);
     rb_define_method(cState, "generate", cState_generate, -1);
-    rb_define_alias(cState, "generate_new", "generate"); // :nodoc:
+    rb_define_method(cState, "generate_new", cState_generate_new, -1); // :nodoc:
 
     rb_define_private_method(cState, "allow_duplicate_key?", cState_allow_duplicate_key_p, 0);
 
diff --git a/ext/json/lib/json/version.rb b/ext/json/lib/json/version.rb
index be5daf4c5b6902..dc01ba290b8cc2 100644
--- a/ext/json/lib/json/version.rb
+++ b/ext/json/lib/json/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module JSON
-  VERSION = '2.15.1'
+  VERSION = '2.15.2'
 end
diff --git a/include/ruby/internal/core/rtypeddata.h b/include/ruby/internal/core/rtypeddata.h
index 8e16c31d998080..bf0f60b9132029 100644
--- a/include/ruby/internal/core/rtypeddata.h
+++ b/include/ruby/internal/core/rtypeddata.h
@@ -360,8 +360,7 @@ struct RTypedData {
     /**
      * This is a `const rb_data_type_t *const` value, with the low bits set:
      *
-     * 1: Always set, to differentiate RTypedData from RData.
-     * 2: Set if object is embedded.
+     * 1: Set if object is embedded.
      *
      * This field  stores various  information about how  Ruby should  handle a
      * data.   This roughly  resembles a  Ruby level  class (apart  from method
diff --git a/lib/unicode_normalize/normalize.rb b/lib/unicode_normalize/normalize.rb
index e67fad187a5fb1..7872f8a0bcffdd 100644
--- a/lib/unicode_normalize/normalize.rb
+++ b/lib/unicode_normalize/normalize.rb
@@ -82,16 +82,22 @@ def self.hangul_comp_one(string)
 
   ## Canonical Ordering
   def self.canonical_ordering_one(string)
-    sorting = string.each_char.collect { |c| [c, CLASS_TABLE[c]] }
-    (sorting.length-2).downto(0) do |i| # almost, but not exactly bubble sort
-      (0..i).each do |j|
-        later_class = sorting[j+1].last
-        if 0<later_class and later_class<sorting[j].last
-          sorting[j], sorting[j+1] = sorting[j+1], sorting[j]
-        end
+    result = ''
+    unordered = []
+    chars = string.chars
+    n = chars.size
+    chars.each_with_index do |char, i|
+      ccc = CLASS_TABLE[char]
+      if ccc == 0
+        unordered.sort!.each { result << chars[it % n] }
+        unordered.clear
+        result << char
+      else
+        unordered << ccc * n + i
       end
     end
-    return sorting.collect(&:first).join('')
+    unordered.sort!.each { result << chars[it % n] }
+    result
   end
 
   ## Normalization Forms for Patterns (not whole Strings)
diff --git a/test/json/json_coder_test.rb b/test/json/json_coder_test.rb
index c7248353769969..fb9d7b30a59a11 100755
--- a/test/json/json_coder_test.rb
+++ b/test/json/json_coder_test.rb
@@ -66,4 +66,14 @@ def test_json_coder_dump_NaN_or_Infinity_loop
     end
     assert_include error.message, "NaN not allowed in JSON"
   end
+
+  def test_nesting_recovery
+    coder = JSON::Coder.new
+    ary = []
+    ary << ary
+    assert_raise JSON::NestingError do
+      coder.dump(ary)
+    end
+    assert_equal '{"a":1}', coder.dump({ a: 1 })
+  end
 end
diff --git a/test/test_unicode_normalize.rb b/test/test_unicode_normalize.rb
index 8789ed92d2aee0..98f46551d33374 100644
--- a/test/test_unicode_normalize.rb
+++ b/test/test_unicode_normalize.rb
@@ -209,4 +209,23 @@ def test_us_ascii
     assert_equal true, ascii_string.unicode_normalized?(:nfkc)
     assert_equal true, ascii_string.unicode_normalized?(:nfkd)
   end
+
+  def test_canonical_ordering
+    a = "\u03B1\u0313\u0300\u0345"
+    a_unordered1 = "\u03B1\u0345\u0313\u0300"
+    a_unordered2 = "\u03B1\u0313\u0345\u0300"
+    u1 = "U\u0308\u0304"
+    u2 = "U\u0304\u0308"
+    s = "s\u0323\u0307"
+    s_unordered = "s\u0307\u0323"
+    o = "\u{1611e}\u{1611e}\u{1611f}"
+    # Actual cases called through String#unicode_normalize
+    assert_equal(s + o, UnicodeNormalize.canonical_ordering_one(s_unordered + o))
+    assert_equal(a[1..], UnicodeNormalize.canonical_ordering_one(a_unordered1[1..]))
+    assert_equal(a[1..] + o, UnicodeNormalize.canonical_ordering_one(a_unordered2[1..] + o))
+    # Artificial cases
+    assert_equal(a + u1 + o + u2 + s, UnicodeNormalize.canonical_ordering_one(a + u1 + o + u2 + s))
+    assert_equal(s[1..] + a + a, UnicodeNormalize.canonical_ordering_one(s_unordered[1..] + a_unordered1 + a_unordered2))
+    assert_equal(o + s + u1 + a + o + a + u2 + o, UnicodeNormalize.canonical_ordering_one(o + s_unordered + u1 + a_unordered1 + o + a_unordered2 + u2 + o))
+  end
 end