Buffer overflow in the DNS resolver code used in libc, glibc, and libbind, as derived from ISC BIND, allows remote malicious DNS servers to cause a denial of service and possibly execute arbitrary code via the stub resolvers.

A buffer overflow vulnerability exists in different implementations of the DNS resolver libraries. A remote attacker able to sent malicious DNS responses could potentially exploit this vulnerability to execute arbitrary code or cause a DoS (Denial of Service) on a vulnerable system. The named daemon itself is not vulnerable to this problem, but this latest version of bind 8 includes fixes to the DNS resolver libraries.

A buffer overflow vulnerability was found in the way that the glibc resolver handles the resolution of network names and addresses via DNS in glibc versions 2.2.5 and earlier. Only systems using the 'dns' entry in the 'networks' database in /etc/nsswitch.conf are vulnerable to this issue. By default, Mandrake Linux has this database set to 'files' and is not vulnerable. Likewise, a similar bug is in the glibc-compat packages which provide compatability for programs compiled against 2.0.x versions of glibc.

A vulnerability was discovered in the BIND9 DNS server in versions prior to 9.2.1. An error condition will trigger the shutdown of the server when the rdataset parameter to the dns_message_findtype() function in message.c is not NULL as expected. This condition causes the server to assert an error message and shutdown the BIND server.
The error condition can be remotely exploited by a special DNS packet.
This can only be used to create a Denial of Service on the server; the error condition is correctly detected, so it will not allow an attacker to execute arbitrary code on the server.

Update :

Sascha Kettler noticed that the version of BIND9 supplied originally was in fact 9.2.1RC1 and mis-labelled as 9.2.1. The packages provided in this update are BIND 9.2.1 final. Likewise, the buffer overflow in the DNS resolver libraries, as noted in MDKSA-2002:043, has also been fixed. Thanks to Bernhard Rosenkraenzer at Red Hat for backporting the patches from 8.3.3 to 9.2.1.

Version 9 of ISC BIND, prior to version 9.2.1, contained a denial of service (DoS) attack vulnerability. Various versions of the ISC BIND resolver libraries are vulnerable to a buffer overflow attack.

ISC BIND (Berkeley Internet Name Domain) is an implementation of the DNS (Domain Name System) protocols. BIND includes a DNS server (named)
-- which resolves hostnames to IP addresses, a resolver library (routines for applications to use when interfacing with DNS), and various tools.

Versions of BIND 9 prior to 9.2.1 have a bug that causes certain requests to the BIND name server to fail an internal consistency check, causing the name server to stop responding to requests. This can be used by a remote attacker to cause a denial of service (DoS) attack against name servers. The Common Vulnerabilities and Exposures project (cve.mitre.org) has assigned the name CVE-2002-0400 to this issue.

A buffer overflow vulnerability exists in multiple implementations of DNS resolver libraries. Applications that utilize vulnerable DNS resolver libraries may be affected. A remote attacker who is able to send malicious DNS responses could potentially exploit this vulnerability to execute arbitrary code or cause a denial of service (DoS) attack on a vulnerable system. Red Hat Linux does not ship with any applications or libraries that link against the BIND resolver libraries; however, third party code may be affected. (CVE-2002-0651)

Red Hat Linux Advanced Server shipped with a version of ISC BIND vulnerable to both of these issues. All users of BIND are advised to upgrade to the errata packages containing BIND 9.2.1 which contains backported patches that correct these issues.

Updated glibc packages are available which fix a buffer overflow in the XDR decoder and two vulnerabilities in the resolver functions.

[updated 8 aug 2002] Updated packages have been made available, as the original errata introduced a bug which could cause calloc() to crash on 32-bit platforms when passed a size of 0. These updated errata packages contain a patch to correct this bug.

The glibc package contains standard libraries which are used by multiple programs on the system. Sun RPC is a remote procedure call framework which allows clients to invoke procedures in a server process over a network. XDR is a mechanism for encoding data structures for use with RPC. NFS, NIS, and other network services that are built upon Sun RPC. The glibc package contains an XDR encoder/decoder derived from Sun's RPC implementation which was recently demonstrated to be vulnerable to a heap overflow.

An error in the calculation of memory needed for unpacking arrays in the XDR decoder can result in a heap buffer overflow in glibc 2.2.5 and earlier. Depending upon the application, this vulnerability may be exploitable and could lead to arbitrary code execution.
(CVE-2002-0391)

A buffer overflow vulnerability has been found in the way the glibc resolver handles the resolution of network names and addresses via DNS (as per Internet RFC 1011). Version 2.2.5 of glibc and earlier versions are affected. A system would be vulnerable to this issue if the 'networks' database in the /etc/nsswitch.conf file includes the 'dns' entry. By default, Red Hat Linux Advanced Server ships with 'networks' set to 'files' and is therefore not vulnerable to this issue. (CVE-2002-0684)

A related issue is a bug in the glibc-compat packages, which provide compatibility for applications compiled against glibc version 2.0.x.
Applications compiled against this version (such as those distributed with early Red Hat Linux releases 5.0, 5.1, and 5.2) could also be vulnerable to this issue. (CVE-2002-0651)

All users should upgrade to these errata packages which contain patches to the glibc libraries and therefore are not vulnerable to these issues.

Thanks to Solar Designer for providing patches for this issue.

ID	Name	Product	Family	Severity
61917	Mandrake Linux Security Advisory : bind (MDKSA-2002:043)	Nessus	Mandriva Local Security Checks	high
13953	Mandrake Linux Security Advisory : glibc (MDKSA-2002:050)	Nessus	Mandriva Local Security Checks	high
13943	Mandrake Linux Security Advisory : bind (MDKSA-2002:038-1)	Nessus	Mandriva Local Security Checks	high
12635	RHEL 2.1 : bind (RHSA-2002:119)	Nessus	Red Hat Local Security Checks	high
12318	RHEL 2.1 : glibc (RHSA-2002:167)	Nessus	Red Hat Local Security Checks	critical

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CVE-2002-0651

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