Array index error in the (1) dtoa implementation in dtoa.c (aka pdtoa.c) and the (2) gdtoa (aka new dtoa) implementation in gdtoa/misc.c in libc, as used in multiple operating systems and products including in FreeBSD 6.4 and 7.2, NetBSD 5.0, OpenBSD 4.5, Mozilla Firefox 3.0.x before 3.0.15 and 3.5.x before 3.5.4, K-Meleon 1.5.3, SeaMonkey 1.1.8, and other products, allows context-dependent attackers to cause a denial of service (application crash) and possibly execute arbitrary code via a large precision value in the format argument to a printf function, which triggers incorrect memory allocation and a heap-based buffer overflow during conversion to a floating-point number.