WebKit in Apple Safari before 4.0, iPhone OS 1.0 through 2.2.1, and iPhone OS for iPod touch 1.1 through 2.2.1 does not initialize a pointer during handling of a Cascading Style Sheets (CSS) attr function call with a large numerical argument, which allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption and application crash) via a crafted HTML document.