WebKit in Apple Safari before 5.0 on Mac OS X 10.5 through 10.6 and Windows, and before 4.1 on Mac OS X 10.4, accesses uninitialized memory during a selection change on a form input element, which allows remote attackers to execute arbitrary code or cause a denial of service (application crash) via a crafted HTML document.
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.