lib/info.c in libvorbis 1.1.2, and possibly other versions before 1.2.0, allows context-dependent attackers to cause a denial of service and possibly execute arbitrary code via invalid (1) blocksize_0 and (2) blocksize_1 values, which trigger a "heap overwrite" in the _01inverse function in res0.c.  NOTE: this issue has been RECAST so that CVE-2007-4029 handles additional vectors.