CoreGraphics in Apple Safari before 4.0 on Windows does not properly use arithmetic during automatic hinting of TrueType fonts, which allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption and application crash) via crafted font data.
http://www.vupen.com/english/advisories/2009/1522
http://www.securityfocus.com/bid/35308
http://support.apple.com/kb/HT3613
http://secunia.com/advisories/35379
http://lists.apple.com/archives/security-announce/2009/jun/msg00002.html