Microsoft Internet Explorer 6 through 9, and 10 Consumer Preview, allows remote attackers to bypass Protected Mode or cause a denial of service (memory corruption) by leveraging access to a Low integrity process, as demonstrated by VUPEN during a Pwn2Own competition at CanSecWest 2012.
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.