From f5902bf7d8397db27ce7c1e06a7c9f243373da9e Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 27 May 2026 22:06:08 +0000
Subject: [PATCH 1/2] Initial plan


From 1941ab69a9d87a27bbbc55b2a884b10bd1a1774a Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 27 May 2026 22:29:10 +0000
Subject: [PATCH 2/2] Add regression tests for
 JsonSerializer.Deserialize<JsonNode> MaxDepth enforcement

Adds tests verifying that JsonSerializer.Deserialize<JsonNode/JsonArray/JsonObject>
correctly throws JsonException when MaxDepth is exceeded for deeply nested arrays and
objects, as reported in the issue.

- DomTests.cs: DeserializeToNode_RespectsMaxDepth_Arrays/_Objects (parallel to
  existing SerializeToNode_RespectsMaxDepth)
- JsonNodeTests.cs: Deserialize_JsonNode_RespectsMaxDepth_DeeplyNestedArrays

Co-authored-by: steveisok <471438+steveisok@users.noreply.github.com>
---
 .../JsonNode/JsonNodeTests.cs                 | 21 +++++++++++
 .../Serialization/DomTests.cs                 | 37 +++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/JsonNode/JsonNodeTests.cs b/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/JsonNode/JsonNodeTests.cs
index 6573f7e9760198..c17579baa2893a 100644
--- a/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/JsonNode/JsonNodeTests.cs
+++ b/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/JsonNode/JsonNodeTests.cs
@@ -3,6 +3,7 @@
 
 using System.Collections;
 using System.Collections.Generic;
+using System.Linq;
 using Xunit;
 
 namespace System.Text.Json.Nodes.Tests
@@ -339,5 +340,25 @@ public static void JsonValue_AsValue()
             JsonValue value = node.AsValue();
             Assert.Equal(42, value.GetValue<int>());
         }
+
+        [Theory]
+        [InlineData(5)]
+        [InlineData(32)]
+        public static void Deserialize_JsonNode_RespectsMaxDepth_DeeplyNestedArrays(int maxDepth)
+        {
+            var options = new JsonSerializerOptions { MaxDepth = maxDepth };
+
+            // Exactly at max depth: should succeed.
+            string withinDepth = string.Concat(Enumerable.Repeat("[", maxDepth))
+                                + string.Concat(Enumerable.Repeat("]", maxDepth));
+            JsonNode? node = JsonSerializer.Deserialize<JsonNode>(withinDepth, options);
+            Assert.NotNull(node);
+            Assert.IsType<JsonArray>(node);
+
+            // One level beyond max depth: must throw JsonException.
+            string beyondDepth = string.Concat(Enumerable.Repeat("[", maxDepth + 1))
+                               + string.Concat(Enumerable.Repeat("]", maxDepth + 1));
+            Assert.Throws<JsonException>(() => JsonSerializer.Deserialize<JsonNode>(beyondDepth, options));
+        }
     }
 }
diff --git a/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/DomTests.cs b/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/DomTests.cs
index bf11f1cbf8b875..23b8df45710a5b 100644
--- a/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/DomTests.cs
+++ b/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/DomTests.cs
@@ -210,6 +210,43 @@ public static void SerializeToNode_RespectsMaxDepth(int maxDepth)
             Assert.Throws<JsonException>(() => JsonSerializer.SerializeToNode(value, options));
         }
 
+        [Theory]
+        [InlineData(5)]
+        [InlineData(32)]
+        [InlineData(70)] // default max depth is 64
+        public static void DeserializeToNode_RespectsMaxDepth_Arrays(int maxDepth)
+        {
+            var options = new JsonSerializerOptions { MaxDepth = maxDepth };
+
+            // Exactly at max depth should succeed.
+            string withinDepth = string.Concat(Enumerable.Repeat("[", maxDepth)) + string.Concat(Enumerable.Repeat("]", maxDepth));
+            JsonNode? node = JsonSerializer.Deserialize<JsonNode>(withinDepth, options);
+            Assert.NotNull(node);
+
+            // One level beyond max depth should throw.
+            string beyondDepth = string.Concat(Enumerable.Repeat("[", maxDepth + 1)) + string.Concat(Enumerable.Repeat("]", maxDepth + 1));
+            Assert.Throws<JsonException>(() => JsonSerializer.Deserialize<JsonNode>(beyondDepth, options));
+            Assert.Throws<JsonException>(() => JsonSerializer.Deserialize<JsonArray>(beyondDepth, options));
+        }
+
+        [Theory]
+        [InlineData(5)]
+        [InlineData(32)]
+        [InlineData(70)] // default max depth is 64
+        public static void DeserializeToNode_RespectsMaxDepth_Objects(int maxDepth)
+        {
+            var options = new JsonSerializerOptions { MaxDepth = maxDepth };
+
+            // Build nested object JSON: {"x":{"x":...{"x":1}...}}
+            string withinDepth = string.Concat(Enumerable.Repeat("{\"x\":", maxDepth)) + "1" + string.Concat(Enumerable.Repeat("}", maxDepth));
+            JsonNode? node = JsonSerializer.Deserialize<JsonNode>(withinDepth, options);
+            Assert.NotNull(node);
+
+            string beyondDepth = string.Concat(Enumerable.Repeat("{\"x\":", maxDepth + 1)) + "1" + string.Concat(Enumerable.Repeat("}", maxDepth + 1));
+            Assert.Throws<JsonException>(() => JsonSerializer.Deserialize<JsonNode>(beyondDepth, options));
+            Assert.Throws<JsonException>(() => JsonSerializer.Deserialize<JsonObject>(beyondDepth, options));
+        }
+
         public class RecursiveClass
         {
             public RecursiveClass? Next { get; set; }