c-ares is an asynchronous resolver library. Versions 1.32.3 through 1.34.5 terminate a query after maximum attempts when using read_answer() and process_answer(), which can cause a Denial of Service. This issue is fixed in version 1.34.6.

c-ares is a C library for asynchronous DNS requests. `ares__read_line()` is used to parse local configuration files such as `/etc/resolv.conf`, `/etc/nsswitch.conf`, the `HOSTALIASES` file, and if using a c-ares version prior to 1.27.0, the `/etc/hosts` file. If any of these configuration files has an embedded `NULL` character as the first character in a new line, it can lead to attempting to read memory prior to the start of the given buffer which may result in a crash. This issue is fixed in c-ares 1.27.0. No known workarounds exist.

Buffer overflow vulnerability in c-ares before 1_16_1 thru 1_17_0 via function ares_parse_soa_reply in ares_parse_soa_reply.c.

A possible use-after-free and double-free in c-ares lib version 1.16.0 if ares_destroy() is called prior to ares_getaddrinfo() completing. This flaw possibly allows an attacker to crash the service that uses c-ares lib. The highest threat from this vulnerability is to this service availability.

The c-ares function `ares_parse_naptr_reply()`, which is used for parsing NAPTR responses, could be triggered to read memory outside of the given input buffer if the passed in DNS response packet was crafted in a particular way.

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.