Heap-based buffer overflow in the ares_create_query function in c-ares 1.x before 1.12.0 allows remote attackers to cause a denial of service (out-of-bounds write) or possibly execute arbitrary code via a hostname with an escaped trailing dot.

The ares_init:randomize_key function in c-ares, on platforms other than Windows, uses a weak facility for producing a random number sequence (Unix rand), which makes it easier for remote attackers to spoof DNS responses by guessing certain values.

c-ares before 1.4.0 uses a predictable seed for the random number generator for the DNS Transaction ID field, which might allow remote attackers to spoof DNS responses by guessing the field value.