diff --git a/ruby-4.0.3-Fix-a-format-string-injection-vulnerability.patch b/ruby-4.0.3-Fix-a-format-string-injection-vulnerability.patch
new file mode 100644
index 0000000..a654e9e
--- /dev/null
+++ b/ruby-4.0.3-Fix-a-format-string-injection-vulnerability.patch
@@ -0,0 +1,86 @@
+From 83dbd3f615bd8e7a31571124059eb3264f73c559 Mon Sep 17 00:00:00 2001
+From: Jean Boussier <jean.boussier@gmail.com>
+Date: Wed, 18 Mar 2026 08:56:17 +0100
+Subject: [PATCH] Fix a format string injection vulnerability
+
+In `JSON.parse(doc, allow_duplicate_key: false)`.
+---
+ ext/json/parser/parser.c      | 26 +++++++++++++++++++-------
+ test/json/json_parser_test.rb |  7 +++++++
+ 2 files changed, 26 insertions(+), 7 deletions(-)
+
+diff --git a/ext/json/parser/parser.c b/ext/json/parser/parser.c
+index 8f9729ef28..a05c5e9657 100644
+--- a/ext/json/parser/parser.c
++++ b/ext/json/parser/parser.c
+@@ -400,14 +400,9 @@ static void emit_parse_warning(const char *message, JSON_ParserState *state)
+
+ #define PARSE_ERROR_FRAGMENT_LEN 32
+
+-#ifdef RBIMPL_ATTR_NORETURN
+-RBIMPL_ATTR_NORETURN()
+-#endif
+-static void raise_parse_error(const char *format, JSON_ParserState *state)
++static VALUE build_parse_error_message(const char *format, JSON_ParserState *state, long line, long column)
+ {
+     unsigned char buffer[PARSE_ERROR_FRAGMENT_LEN + 3];
+-    long line, column;
+-    cursor_position(state, &line, &column);
+
+     const char *ptr = "EOF";
+     if (state->cursor && state->cursor < state->end) {
+@@ -442,11 +437,23 @@ static void raise_parse_error(const char *format, JSON_ParserState *state)
+     VALUE msg = rb_sprintf(format, ptr);
+     VALUE message = rb_enc_sprintf(enc_utf8, "%s at line %ld column %ld", RSTRING_PTR(msg), line, column);
+     RB_GC_GUARD(msg);
++    return message;
++}
+
++static VALUE parse_error_new(VALUE message, long line, long column)
++{
+     VALUE exc = rb_exc_new_str(rb_path2class("JSON::ParserError"), message);
+     rb_ivar_set(exc, rb_intern("@line"), LONG2NUM(line));
+     rb_ivar_set(exc, rb_intern("@column"), LONG2NUM(column));
+-    rb_exc_raise(exc);
++    return exc;
++}
++
++NORETURN(static) void raise_parse_error(const char *format, JSON_ParserState *state)
++{
++    long line, column;
++    cursor_position(state, &line, &column);
++    VALUE message = build_parse_error_message(format, state, line, column);
++    rb_exc_raise(parse_error_new(message, line, column));
+ }
+
+ #ifdef RBIMPL_ATTR_NORETURN
+@@ -896,6 +903,11 @@ static void raise_duplicate_key_error(JSON_ParserState *state, VALUE duplicate_k
+         rb_inspect(duplicate_key)
+     );
+
++    long line, column;
++    cursor_position(state, &line, &column);
++    rb_str_concat(message, build_parse_error_message("", state, line, column)) ;
++    rb_exc_raise(parse_error_new(message, line, column));
++
+     raise_parse_error(RSTRING_PTR(message), state);
+     RB_GC_GUARD(message);
+ }
+diff --git a/test/json/json_parser_test.rb b/test/json/json_parser_test.rb
+index ec9391909d..61ea35d1f9 100644
+--- a/test/json/json_parser_test.rb
++++ b/test/json/json_parser_test.rb
+@@ -411,6 +411,13 @@ def test_parse_duplicate_key
+     end
+   end
+
++  def test_parse_duplicate_key_escape
++    error = assert_raise(ParserError) do
++      JSON.parse('{"%s%s%s%s":1,"%s%s%s%s":2}', allow_duplicate_key: false)
++    end
++    assert_match "%s%s%s%s", error.message
++  end
++
+   def test_some_wrong_inputs
+     assert_raise(ParserError) { parse('[] bla') }
+     assert_raise(ParserError) { parse('[] 1') }
diff --git a/ruby4.0.spec b/ruby4.0.spec
index 09aad9e..887734f 100644
--- a/ruby4.0.spec
+++ b/ruby4.0.spec
@@ -335,6 +335,12 @@ Patch10: ruby-4.0.1-test_box-avoid-failure-with-program-suffix.patch
 # option in Ruby's main build.
 # https://github.com/brianmario/mysql2/issues/1201
 Patch11: rubygem-mysql2-0.5.7-Disable-RPATH-completely-in-extconf.rb.patch
+# CVE-2026-33210
+# Fix for Denial of Service or Information Disclosure
+# via format string injection
+# in Ruby JSON
+# https://github.com/ruby/json/commit/393b41c3e5f87491e1e34fa59fa78ff6fa179a74
+Patch12: ruby-4.0.3-Fix-a-format-string-injection-vulnerability.patch
 
 %{?with_rubypick:Suggests: rubypick}
 
@@ -498,6 +504,7 @@ popd
 %patch 7 -p1
 %patch 8 -p1
 %patch 10 -p1
+%patch 12 -p1
 
 # Provide an example of usage of the tapset:
 cp -a %{SOURCE3} .
@@ -1645,6 +1652,9 @@ make -C %{_vpath_builddir} runruby TESTRUN_SCRIPT=" \
 - Fix ERB: Arbitrary code execution via deserialization bypass
  (CVE-2026-41316)
   Resolves: RHEL-170911
+- Fix JSON: Denial of Service or Information Disclosure via format string injection
+ (CVE-2026-33210)
+ Resolves: RHEL-169964
 
 * Thu Feb 05 2026 Jarek Prokop <jprokop@redhat.com> - 4.0.1-33
 - Initial package.