Buffer overflow in CHICKEN 4.9.0.x before 4.9.0.2, 4.9.x before 4.9.1, and before 5.0 allows attackers to have unspecified impact via a positive START argument to the "substring-index[-ci] procedures."

Buffer overflow in the "read-u8vector!" procedure in the srfi-4 unit in CHICKEN stable 4.8.0.7 and development snapshots before 4.9.1 allows remote attackers to cause a denial of service (memory corruption and application crash) and possibly execute arbitrary code via a "#f" value in the NUM argument.