Software Engineering Institute

There is a buffer overflow in the processing of NXT records in the routine rrextract, part of the file ns_resp.c. Specifically, in vulnerable versions of BIND, there is a section of code which reads:

case T_NXT:
n = dn_expand(msg, eom, cp, (char *)data, sizeof data);
if (n < 0) {
hp->rcode = FORMERR;
return (-1);
}
if (!ns_nameok((char *)data, class, NULL, response_trans,
domain_ctx, dname, from.sin_addr)) {
hp->rcode = FORMERR;
return (-1);
}
cp += n;
cp1 = data + strlen((char *)data) + 1;
memcpy(cp1, cp, dlen - n);

The value of the dlen can be influenced by an intruder in such a way that the expression 'dlen - n' is larger than the size allocated to cp1. Further, the contents of cp can be influenced by an intruder. Thus, this vulnerability can be exploited to execute arbitrary code with the privileges of the process running named.

An exploit for this vulnerability is publicly available .

NXT record processing was introduced to BIND in version 8.2. 8.1.2 and earlier (including 4.9.x) do not appear to be vulnerable to this problem.

Remote user may gain default process access of local nameserver, usually root

Upgrade to the latest version of BIND.