Vulnerability Note VU#16532

BIND T_NXT record processing may cause buffer overflow

Original Release date: 28 Jan 2001 | Last revised: 03 Feb 2006


A vulnerability in BIND, repaired in verison 8.2.2p5, allows remote attackers to execute code with the privileges of the process running named. This vulnerability was widely exploited from November 1999 to December 2000.


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.

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
The SCO Group (SCO Unix)Affected-28 Jan 2001
FujitsuNot Affected-28 Jan 2001
Sun Microsystems, Inc.Not Affected-28 Jan 2001
Compaq Computer CorporationUnknown-28 Jan 2001
Data GeneralUnknown-28 Jan 2001
If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A N/A



Our thanks to ISC for assistance in understanding this vulnerability.

This document was written by Shawn V Hernan.

Other Information

  • CVE IDs: CVE-1999-0833
  • CERT Advisory: CA-1999-14
  • Date Public: 10 Nov 99
  • Date First Published: 28 Jan 2001
  • Date Last Updated: 03 Feb 2006
  • Severity Metric: 108.16
  • Document Revision: 7


If you have feedback, comments, or additional information about this vulnerability, please send us email.