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BIND T_NXT record processing may cause buffer overflow

Vulnerability Note VU#16532

Original Release Date: 2001-01-28 | Last Revised: 2006-02-03

Overview

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.

Description

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.

Impact

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

Solution

Upgrade to the latest version of BIND.

Vendor Information

16532
 

CVSS Metrics

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References

Acknowledgements

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
Severity Metric: 108.16
Date Public: 1999-11-10
Date First Published: 2001-01-28
Date Last Updated: 2006-02-03 22:28 UTC
Document Revision: 7

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