Integer overflow in the CFDataReplaceBytes function in the CFData API in CoreFoundation in Apple Mac OS X before 10.5.3 allows context-dependent attackers to execute arbitrary code or cause a denial of service (crash) via an invalid length argument, which triggers a heap-based buffer overflow.

More... (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2008-1030)