Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
===========================================================================
AUSCERT External Security Bulletin Redistribution
ESB-2006.0093 -- [FreeBSD]
Infinite loop in SACK handling
2 February 2006
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: kernel
Publisher: FreeBSD
Operating System: FreeBSD
Impact: Denial of Service
Access: Remote/Unauthenticated
CVE Names: CVE-2006-0433
Original Bulletin:
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-06:08.sack.asc
- --------------------------BEGIN INCLUDED TEXT--------------------
- -----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
=============================================================================
FreeBSD-SA-06:08.sack Security Advisory
The FreeBSD Project
Topic: Infinite loop in SACK handling
Category: core
Module: netinet
Announced: 2006-02-01
Credits: Scott Wood
Affects: FreeBSD 5.3 and 5.4
Corrected: 2006-01-24 01:16:18 UTC (RELENG_5, 5.4-STABLE)
2006-02-01 19:43:10 UTC (RELENG_5_4, 5.4-RELEASE-p11)
2006-02-01 19:43:36 UTC (RELENG_5_3, 5.3-RELEASE-p26)
CVE Name: CVE-2006-0433
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
SACK (Selective Acknowledgement) is an extension to the TCP/IP protocol
that allows hosts to acknowledge the receipt of some, but not all, of
the packets sent, thereby reducing the cost of retransmissions.
II. Problem Description
When insufficient memory is available to handle an incoming selective
acknowledgement, the TCP/IP stack may enter an infinite loop.
III. Impact
By opening a TCP connection and sending a carefully crafted series of
packets, an attacker may be able to cause a denial of service.
IV. Workaround
On FreeBSD 5.4, the net.inet.tcp.sack.enable sysctl can be used to
disable the use of SACK:
# sysctl net.inet.tcp.sack.enable=0
No workaround is available for FreeBSD 5.3.
V. Solution
Perform one of the following:
1) Upgrade your vulnerable system to 5-STABLE or to the RELENG_5_4 or
RELENG_5_3 security branch dated after the correction date.
2) To patch your present system:
The following patch have been verified to apply to FreeBSD 5.3 and
5.4 systems.
a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-06:08/sack.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-06:08/sack.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_5
src/sys/netinet/tcp_sack.c 1.3.2.10
RELENG_5_4
src/UPDATING 1.342.2.24.2.20
src/sys/conf/newvers.sh 1.62.2.18.2.16
src/sys/netinet/tcp_sack.c 1.3.2.5.2.1
RELENG_5_3
src/UPDATING 1.342.2.13.2.29
src/sys/conf/newvers.sh 1.62.2.15.2.31
src/sys/netinet/tcp_sack.c 1.3.4.1
- - -------------------------------------------------------------------------
VII. References
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-0433
The latest revision of this advisory is available at
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-06:08.sack.asc
- -----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.2 (FreeBSD)
iD8DBQFD4RCIFdaIBMps37IRAplNAJ9sEJf5VkMOJaWO7P/wNHEzzW1aqACfcAfL
e95PJAa1af/klNC+fZEipnY=
=yZbN
- -----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
iQCVAwUBQ+GOTyh9+71yA2DNAQL6OgQAkjQ7fsJb2YqHFtnO6MP+D9ARr70sqHO6
4CtCF7psUJrEE81odzZ4MkDDs50Z01Z/cxr3qeQIK0iNHe7VeN/61N4B0uxyQuHm
AdMvtOjLY59w4Sq2soWFWnB6ST1gzqKkGUAIZkGAQmR7fmgHHzrJ6ntuFX2GKGsA
Azb1/0P+E2Q=
=oy+e
-----END PGP SIGNATURE-----