Multiple use-after-free vulnerabilities in WebKit in Apple Safari before 5.0.1 on Mac OS X 10.5 through 10.6 and Windows, and before 4.1.1 on Mac OS X 10.4; and webkitgtk before 1.2.6; allow remote attackers to execute arbitrary code or cause a denial of service (application crash) via a (1) font-face or (2) use element in an SVG document.