diff --git a/third_party/blink/renderer/platform/video_capture/video_capture_impl.cc b/third_party/blink/renderer/platform/video_capture/video_capture_impl.cc
--- a/third_party/blink/renderer/platform/video_capture/video_capture_impl.cc
+++ b/third_party/blink/renderer/platform/video_capture/video_capture_impl.cc
@@ -289,6 +289,19 @@ bool VideoCaptureImpl::ProcessBuffer(
             (media::VideoFrame::NumPlanes(
                  video_frame_init_data.ready_buffer->info->pixel_format) == 3))
             << "Currently, only YUV formats support custom strides.";
+        // Reject strides that are narrower than a row: WrapExternalYuvData()
+        // does not validate stride >= RowBytes(width), and downstream
+        // consumers that copy coded_size.width() bytes per row would read
+        // past the mapped data.
+        for (size_t plane = 0; plane < 3; ++plane) {
+          const size_t row_bytes = media::VideoFrame::RowBytes(
+              plane, video_frame_init_data.ready_buffer->info->pixel_format,
+              video_frame_init_data.ready_buffer->info->coded_size.width());
+          if (video_frame_init_data.ready_buffer->info->strides
+                  ->stride_by_plane[plane] < row_bytes) {
+            return false;
+          }
+        }
         const size_t y_size =
             (media::VideoFrame::Rows(
                  media::VideoFrame::Plane::kY,