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.
The product reads from a buffer using buffer access mechanisms such as indexes or pointers that reference memory locations prior to the targeted buffer.