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 the handling of a use element in an SVG document, which allows remote attackers to execute arbitrary code or cause a denial of service (application crash) via a crafted document containing XML that triggers a parsing error, related to ProcessInstruction.
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.