> resolvconf(8) is a shell script which does not validate its input. A lack of quoting meant that shell commands pass as input to resolvconf(8) may be executed.

The fix consists of implementing an XXX present since the code was added:

    /*
     * XXX validate that domain name only contains valid characters
     * for two reasons: 1) correctness, 2) we do not want to pass
     * possible malicious, unescaped characters like `` to a script
     * or program that could be exploited that way.
     */