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                 NetBSD Security Advisory 1998-001
                 ---------------------------------

Topic:		BIND 4.9.6 vulnerabilities
Version:	All current versions of NetBSD
Severity:	Problem may allow remote privileged access, or cause
		a denial of service.


Abstract
- --------

Several problems have been found in BIND 4.9.6.  One involves a buffer
overflow in the inverse query code, which is not enabled by default.
The others are similar buffer overflows in the rest of the code.
Depending on other site configuration specifics, several of these
overflows could contribute to an exploit designed to allow remote
super-user access to the system.


Technical Details
- -----------------

Both of the problems described below are solved in both BIND 4.9.7
and BIND 8.1.2.

The BIND 4.9.6 release does not properly bounds check a memory copy
when responding to an inverse query request.  Improperly or maliciously
formatted inverse query requests can cause named to overwrite its'
stack, granting root access to a remote attacker.

There are also many other occurances of improper bounds checking of
memory copy operations, in both named and many of the DNS utilities
(eg, dig(1) and nslookup(1)).  These problems may cause the server
to attempt to read invalid memory locations, causing the server to
crash or return garbage answers.


Solutions and Workarounds
- -------------------------

As NetBSD does not ship with the inverse query option enabled by
default, most NetBSD sites will not be affected by this problem.  If
there is a line containing `fake-iquery' in the /etc/namedb/named.boot,
or named has been built with the `INVQ' option defined in the
src/usr.sbin/named/conf/options.h file, then the server is vulnerable
to this problem. Removing `fake-iquery' from the named.boot or
undefining `INVQ' will close this problem immediately.

The second problem is only fixed by either patching and rebuilding
NetBSD sources with the patch below, or manually upgrading to a newer
version of BIND (4.9.7 or 8.1.2).

A patch has been made available for NetBSD 1.3 and 1.3.1, and can be
found on the NetBSD FTP server:
    ftp://ftp.NetBSD.ORG/pub/NetBSD/misc/security/patches/19980506-bind


Thanks To
- ---------

Many thanks go to CERT and to the Internet Software Consortium for
providing the NetBSD Project with this information.  Please see
http://www.cert.org/ and http://www.isc.org/ for more information.


More Information
- ----------------

Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.ORG/ and http://www.NetBSD.ORG/Security/.


Copyright 1998, The NetBSD Foundation.  All Rights Reserved.

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