Use-after-free vulnerability in Blink, as used in Google Chrome before 38.0.2125.101, allows remote attackers to cause a denial of service or possibly have unspecified other impact via crafted JavaScript code that triggers a widget-position update that improperly interacts with the render tree, related to the FrameView::updateLayoutAndStyleForPainting function in core/frame/FrameView.cpp and the RenderLayerScrollableArea::setScrollOffset function in core/rendering/RenderLayerScrollableArea.cpp.
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.