PatchGap
Chrome · Geometry

CVE-2026-87458

Logic Error in Geometry
Medium chrome Logic Error 🔧 Commit mapped

Overview

Medium
Severity
—
CVSS
No
Exploited ITW
Fixed
Fix Status
ImpactUI misrepresentation in Geometry
DescriptionUI misrepresentation in Geometry
ComponentGeometry
Bug ClassLogic Error
Tracker517072005
Fix commita0ceaf275d46 (chromium/src) +70/-1
CISA KEVNot listed
CreditedGoogle
Disclosed2026-09-08

Changed Functions

FunctionChangeNotes
TEST_F
third_party/blink/renderer/core/intersection_observer/intersection_observer_test.cc
 modified

Files Changed

  • third_party/blink/renderer/core/intersection_observer/intersection_observer_test.cc
  • third_party/blink/renderer/core/paint/paint_layer.cc

Patch

view commit
From a0ceaf275d46280067394f9f8e61c4a90df61f6f Mon Sep 17 00:00:00 2001
From: Stefan Zager <[email protected]>
Date: Tue, 28 Jul 2026 17:45:46 -0700
Subject: [PATCH] Fix hit testing depth order when testing children

This CL:

https://chromium-review.googlesource.com/c/chromium/src/+/7442380

... missed one location for using container_transform_state instead of
local_transform_state.

Bug: 464173566,517072005
Change-Id: Ia33ad813f3f89b35562f0fcd3c154675c2801163
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/8128190
Reviewed-by: Philip Rogers <[email protected]>
Commit-Queue: Philip Rogers <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1669908}
---

diff --git a/third_party/blink/renderer/core/intersection_observer/intersection_observer_test.cc b/third_party/blink/renderer/core/intersection_observer/intersection_observer_test.cc
index c7f4d5a..339a52f 100644
--- a/third_party/blink/renderer/core/intersection_observer/intersection_observer_test.cc
+++ b/third_party/blink/renderer/core/intersection_observer/intersection_observer_test.cc
@@ -2871,6 +2871,71 @@
   EXPECT_FALSE(observer_delegate->LastEntry()->isVisible());
 }
 
+TEST_F(IntersectionObserverV2Test, Preserve3DOcclusion) {
+  WebView().MainFrameViewWidget()->Resize(gfx::Size(800, 600));
+  SimRequest main_resource("https://example.com/", "text/html");
+  LoadURL("https://example.com/");
+  main_resource.Complete(R"HTML(
+    <style>
+      #GP {
+        transform: translateX(0);
+        transform-style: preserve-3d;
+      }
+      #TC {
+        position: absolute;
+        width: 1px; height: 1px;
+        transform: translateZ(5px);
+        transform-style: preserve-3d;
+      }
+      #L {
+        position: absolute;
+        width: 1px; height: 1px;
+        isolation: isolate;
+      }
+      #occluder, #target {
+        position: absolute;
+        left: 100px; top: 100px;
+        width: 100; height: 100;
+      }
+    </style>
+    <div id="GP">
+      <div id="TC">
+        <div>
+          <div id="L">
+            <div id="occluder"></div>
+          </div>
+        </div>
+      </div>
+      <div id="target"></div>
+    </div>
+  )HTML");
+  Compositor().BeginFrame();
+
+  IntersectionObserverInit* observer_init = IntersectionObserverInit::Create();
+  observer_init->setTrackVisibility(true);
+  observer_init->setDelay(100);
+  DummyExceptionStateForTesting exception_state;
+  TestIntersectionObserverDelegate* observer_delegate =
+      MakeGarbageCollected<TestIntersectionObserverDelegate>(GetDocument());
+  IntersectionObserver* observer = IntersectionObserver::Create(
+      observer_init, *observer_delegate,
+      LocalFrameUkmAggregator::kJavascriptIntersectionObserver,
+      exception_state);
+  ASSERT_FALSE(exception_state.HadException());
+  Element* target = GetDocument().getElementById(AtomicString("target"));
+  ASSERT_TRUE(target);
+  observer->observe(target);
+
+  Compositor().BeginFrame();
+  test::RunPendingTasks();
+  ASSERT_FALSE(Compositor().NeedsBeginFrame());
+  EXPECT_EQ(observer_delegate->CallCount(), 1);
+  EXPECT_EQ(observer_delegate->EntryCount(), 1);
+  EXPECT_TRUE(observer_delegate->LastEntry()->isIntersecting());
+  // #target is occluded by #occluder which is in front of it (z=5 vs z=0).
+  EXPECT_FALSE(observer_delegate->LastEntry()->isVisible());
+}
+
 TEST_F(IntersectionObserverV2Test, TableCellOcclusion) {
   WebView().MainFrameViewWidget()->Resize(gfx::Size(800, 600));
   SimRequest main_resource("https://example.com/", "text/html");
diff --git a/third_party/blink/renderer/core/paint/paint_layer.cc b/third_party/blink/renderer/core/paint/paint_layer.cc
index 3b4d36c..597eada 100644
--- a/third_party/blink/renderer/core/paint/paint_layer.cc
+++ b/third_party/blink/renderer/core/paint/paint_layer.cc
@@ -1976,7 +1976,11 @@
     }
 
     if (IsHitCandidateForDepthOrder(
-            hit_layer, depth_sort_descendants, z_offset, local_transform_state,
+            hit_layer, depth_sort_descendants, z_offset,
+            RuntimeEnabledFeatures::
+                    HitTestContainerTransformStateForPreserve3dEnabled()
+                ? container_transform_state
+                : local_transform_state,
             result.GetHitTestRequest().IsHitTestVisualOverflow())) {
       result_layer = hit_layer;
       if (!result.GetHitTestRequest().ListBased())
Loading diff…

Regression Test / PoC

shipped with the fix
diff --git a/third_party/blink/renderer/core/intersection_observer/intersection_observer_test.cc b/third_party/blink/renderer/core/intersection_observer/intersection_observer_test.cc
index c7f4d5a..339a52f 100644
--- a/third_party/blink/renderer/core/intersection_observer/intersection_observer_test.cc
+++ b/third_party/blink/renderer/core/intersection_observer/intersection_observer_test.cc
@@ -2871,6 +2871,71 @@
   EXPECT_FALSE(observer_delegate->LastEntry()->isVisible());
 }
 
+TEST_F(IntersectionObserverV2Test, Preserve3DOcclusion) {
+  WebView().MainFrameViewWidget()->Resize(gfx::Size(800, 600));
+  SimRequest main_resource("https://example.com/", "text/html");
+  LoadURL("https://example.com/");
+  main_resource.Complete(R"HTML(
+    <style>
+      #GP {
+        transform: translateX(0);
+        transform-style: preserve-3d;
+      }
+      #TC {
+        position: absolute;
+        width: 1px; height: 1px;
+        transform: translateZ(5px);
+        transform-style: preserve-3d;
+      }
+      #L {
+        position: absolute;
+        width: 1px; height: 1px;
+        isolation: isolate;
+      }
+      #occluder, #target {
+        position: absolute;
+        left: 100px; top: 100px;
+        width: 100; height: 100;
+      }
+    </style>
+    <div id="GP">
+      <div id="TC">
+        <div>
+          <div id="L">
+            <div id="occluder"></div>
+          </div>
+        </div>
+      </div>
+      <div id="target"></div>
+    </div>
+  )HTML");
+  Compositor().BeginFrame();
+
+  IntersectionObserverInit* observer_init = IntersectionObserverInit::Create();
+  observer_init->setTrackVisibility(true);
+  observer_init->setDelay(100);
+  DummyExceptionStateForTesting exception_state;
+  TestIntersectionObserverDelegate* observer_delegate =
+      MakeGarbageCollected<TestIntersectionObserverDelegate>(GetDocument());
+  IntersectionObserver* observer = IntersectionObserver::Create(
+      observer_init, *observer_delegate,
+      LocalFrameUkmAggregator::kJavascriptIntersectionObserver,
+      exception_state);
+  ASSERT_FALSE(exception_state.HadException());
+  Element* target = GetDocument().getElementById(AtomicString("target"));
+  ASSERT_TRUE(target);
+  observer->observe(target);
+
+  Compositor().BeginFrame();
+  test::RunPendingTasks();
+  ASSERT_FALSE(Compositor().NeedsBeginFrame());
+  EXPECT_EQ(observer_delegate->CallCount(), 1);
+  EXPECT_EQ(observer_delegate->EntryCount(), 1);
+  EXPECT_TRUE(observer_delegate->LastEntry()->isIntersecting());
+  // #target is occluded by #occluder which is in front of it (z=5 vs z=0).
+  EXPECT_FALSE(observer_delegate->LastEntry()->isVisible());
+}
+
 TEST_F(IntersectionObserverV2Test, TableCellOcclusion) {
   WebView().MainFrameViewWidget()->Resize(gfx::Size(800, 600));
   SimRequest main_resource("https://example.com/", "text/html");
Loading diff…

Original Bug Report

The reporter's bug is still restricted on the tracker. Chrome de-restricts security bugs ~30–90 days after the fix ships; a later run will backfill it here.
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