Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
===========================================================================
AUSCERT External Security Bulletin Redistribution
ESB-2006.0156 -- [FreeBSD]
Remote denial of service in NFS server
2 March 2006
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: sys_nfsserver
Publisher: FreeBSD
Operating System: FreeBSD
Impact: Denial of Service
Access: Remote/Unauthenticated
CVE Names: CVE-2006-0900
Original Bulletin:
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-06:10.nfs.asc
- --------------------------BEGIN INCLUDED TEXT--------------------
- -----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
=============================================================================
FreeBSD-SA-06:10.nfs Security Advisory
The FreeBSD Project
Topic: Remote denial of service in NFS server
Category: core
Module: sys_nfsserver
Announced: 2006-03-01
Credits: Evgeny Legerov
Affects: All FreeBSD releases.
Corrected: 2006-03-01 14:18:11 UTC (RELENG_6, 6.1-PRERELEASE)
2006-03-01 14:18:46 UTC (RELENG_6_0, 6.0-RELEASE-p5)
2006-03-01 14:19:48 UTC (RELENG_5, 5.5-PRERELEASE)
2006-03-01 14:21:01 UTC (RELENG_5_4, 5.4-RELEASE-p12)
2006-03-01 14:24:52 UTC (RELENG_5_3, 5.3-RELEASE-p27)
2006-03-01 14:21:56 UTC (RELENG_4, 4.11-STABLE)
2006-03-01 14:22:30 UTC (RELENG_4_11, 4.11-RELEASE-p15)
2006-03-01 14:23:07 UTC (RELENG_4_10, 4.10-RELEASE-p21)
CVE Name: CVE-2006-0900
For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit
<URL:http://www.freebsd.org/security/>.
I. Background
The Network File System (NFS) allows a host to export some or all of
its filesystems so that other hosts can access them over the network
and mount them as if they were on local disks. NFS is built on top of
the Sun Remote Procedure Call (RPC) framework.
II. Problem Description
A part of the NFS server code charged with handling incoming RPC
messages via TCP had an error which, when the server received a
message with a zero-length payload, would cause a NULL pointer
dereference which results in a kernel panic. The kernel will only
process the RPC messages if a userland nfsd daemon is running.
III. Impact
The NULL pointer deference allows a remote attacker capable of sending
RPC messages to an affected FreeBSD system to crash the FreeBSD system.
IV. Workaround
1) Disable the NFS server: set the nfs_server_enable variable to "NO"
in /etc/rc.conf, and reboot.
Alternatively, if there are no active NFS clients (as listed by the
showmount(8) utility), simply killing the mountd and nfsd processes
should suffice.
2) Add firewall rules to block RPC traffic to the NFS server from
untrusted hosts.
V. Solution
Perform one of the following:
1) Upgrade your vulnerable system to 4-STABLE, 5-STABLE, or 6-STABLE,
or to the RELENG_6_0, RELENG_5_4, RELENG_5_3, RELENG_4_11, or
RELENG_4_10 security branch dated after the correction date.
2) To patch your present system:
The following patches have been verified to apply to FreeBSD 4.10,
4.11, 5.3, 5.4, and 6.0 systems.
a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.
[FreeBSD 4.x]
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-06:10/nfs4.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-06:10/nfs4.patch.asc
[FreeBSD 5.x and 6.x]
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-06:10/nfs.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-06:10/nfs.patch.asc
b) Apply the patch.
# cd /usr/src
# patch < /path/to/patch
c) Recompile your kernel as described in
<URL:http://www.freebsd.org/handbook/kernelconfig.html> and reboot the
system.
VI. Correction details
The following list contains the revision numbers of each file that was
corrected in FreeBSD.
Branch Revision
Path
- - -------------------------------------------------------------------------
RELENG_4
src/sys/nfs/nfs_socket.c 1.60.2.7
RELENG_4_11
src/UPDATING 1.73.2.91.2.16
src/sys/conf/newvers.sh 1.44.2.39.2.19
src/sys/nfs/nfs_socket.c 1.60.2.6.6.1
RELENG_4_10
src/UPDATING 1.73.2.90.2.22
src/sys/conf/newvers.sh 1.44.2.34.2.23
src/sys/nfs/nfs_socket.c 1.60.2.6.4.1
RELENG_5
src/sys/nfsserver/nfs_srvsock.c 1.92.2.2
RELENG_5_4
src/UPDATING 1.342.2.24.2.21
src/sys/conf/newvers.sh 1.62.2.18.2.17
src/sys/nfsserver/nfs_srvsock.c 1.92.2.1.2.1
RELENG_5_3
src/UPDATING 1.342.2.13.2.30
src/sys/conf/newvers.sh 1.62.2.15.2.32
src/sys/nfsserver/nfs_srvsock.c 1.92.4.1
RELENG_6
src/sys/nfsserver/nfs_srvsock.c 1.94.2.1
RELENG_6_0
src/UPDATING 1.416.2.3.2.10
src/sys/conf/newvers.sh 1.69.2.8.2.6
src/sys/nfsserver/nfs_srvsock.c 1.94.4.1
- - -------------------------------------------------------------------------
VII. References
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-0900
The latest revision of this advisory is available at
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-06:10.nfs.asc
- -----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.2 (FreeBSD)
iD8DBQFEBbOIFdaIBMps37IRAgmUAJ0fYEjr1gk8KpHGbcmhpPwh+GqI3ACcDH5X
dN3ngWsO1Z91GdTjJe0e7VE=
=GCDX
- -----END PGP SIGNATURE-----
- --------------------------END INCLUDED TEXT--------------------
You have received this e-mail bulletin as a result of your organisation's
registration with AusCERT. The mailing list you are subscribed to is
maintained within your organisation, so if you do not wish to continue
receiving these bulletins you should contact your local IT manager. If
you do not know who that is, please send an email to auscert@auscert.org.au
and we will forward your request to the appropriate person.
NOTE: Third Party Rights
This security bulletin is provided as a service to AusCERT's members. As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content. The decision to follow or act on information or advice
contained in this security bulletin is the responsibility of each user or
organisation, and should be considered in accordance with your organisation's
site policies and procedures. AusCERT takes no responsibility for consequences
which may arise from following or acting on information or advice contained in
this security bulletin.
NOTE: This is only the original release of the security bulletin. It may
not be updated when updates to the original are made. If downloading at
a later date, it is recommended that the bulletin is retrieved directly
from the author's website to ensure that the information is still current.
Contact information for the authors of the original document is included
in the Security Bulletin above. If you have any questions or need further
information, please contact them directly.
Previous advisories and external security bulletins can be retrieved from:
http://www.auscert.org.au/render.html?cid=1980
If you believe that your computer system has been compromised or attacked in
any way, we encourage you to let us know by completing the secure National IT
Incident Reporting Form at:
http://www.auscert.org.au/render.html?it=3192
===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072
Internet Email: auscert@auscert.org.au
Facsimile: (07) 3365 7031
Telephone: (07) 3365 4417 (International: +61 7 3365 4417)
AusCERT personnel answer during Queensland business hours
which are GMT+10:00 (AEST).
On call after hours for member emergencies only.
===========================================================================
-----BEGIN PGP SIGNATURE-----
Comment: http://www.auscert.org.au/render.html?it=1967
iQCVAwUBRAZatyh9+71yA2DNAQJZPgP8D5GaJfO5yzEQj9lRL+5twLfvAB/nUaIo
+w+cPbOUFW4CXCdjx/Z/GI5afKyffOSNnqOe9AZjPGeHS77Bc8GTbS0duV8UsP0v
XgjRpE6lVSsdSd/lOOcAlGOIXcS+Hf1IrEm10Oa1y0GutImDfh4DJwa/ieI3wfFF
KcFOqrkMIEA=
=fKY0
-----END PGP SIGNATURE-----