[security bulletin] SSRT4884 rev.5 - HP-UX TCP/IP Remote Denial of Service (DoS) Jul 25 2005 06:53PM
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SSRT4884 rev.5 - HP-UX TCP/IP Remote Denial of Service (DoS)

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Bulletin provided that it remains complete and intact.

The information in this Security Bulletin should be acted upon
as soon as possible.

24 July 2005

Remote Denial of Service (DoS)

Hewlett-Packard Company
HP Software Security Response Team

A potential security vulnerability has been identified with HP-UX
running TCP/IP. This vulnerability could be remotely exploited by
an unauthorized user to cause a Denial of Service(DoS).

NISCC VU#532967, CAN-2004-0790, CAN-2004-0791, CAN-2004-1060

SUPPORTED SOFTWARE VERSIONS*: ONLY impacted versions are listed.
HP-UX B.11.00, B.11.04, B.11.11, B.11.22, B.11.23 running TCP/IP.
HP-UX B.11.11 and B.11.23 running TOUR (Transport Optional Upgrade


As reported in NISCC VU#532967 ICMP messages may be used to attack
TCP/IP connections.


There are three issues reported in NISCC VU#532967:

CVE number: CAN-2004-0790
CVE number: CAN-2004-0791
CVE number: CAN-2004-1060


HP-UX B.11.00
->action: install PHNE_33395, optionally set ip_pmtu_strategy=0

HP-UX B.11.04
action: set ip_pmtu_strategy=0 and filter ICMP

HP-UX B.11.11
->action: install PHNE_33159, optionally set ip_pmtu_strategy=0

HP-UX B.11.22
->action: install binary files, optionally set ip_pmtu_strategy=0

HP-UX B.11.23
->action: install PHNE_32606, optionally set ip_pmtu_strategy=0

HP-UX B.11.11
HP-UX B.11.23
action: set ip_pmtu_strategy=0 and filter ICMP


Note: The latest TOUR (Transport Optional Upgrade Release),
version 2.4, is available on B.11.11 only. The latest
Transport Functionality is available to B.11.23 customers
in the HP-UX 11i v2 September 2004 release. Customers
using TOUR on B.11.23 can apply the workaround (set
ip_pmtu_strategy= 0 and filter ICMP) or upgrade to the
HP-UX 11i v2 September 2004 release. After upgrading the
action for B.11.23 Networking.NET2-KRN listed above should
be implemented.

->Patches are available for the core network product
->from <http://itrc.hp.com>:

-> For B.11.00 - PHNE_33395 or subsequent
-> For B.11.11 - PHNE_33159 or subsequent
-> For B.11.23 - PHNE_32606 or subsequent

->Binary files are available for B.11.22 (details are below).

->Optionally set ip_pmtu_strategy=0. Please see the discussion
->below, "Workaround for CAN-2004-1060 may not be necessary."

Until binary files are available for B.11.04 the workarounds below
should be used.

Note: If the TOUR (Transport Optional Upgrade Release) product is
installed the binary files cannot be used.

Until the TOUR product is revised there are several options:

1. Use the workarounds.
->2. Remove TOUR and install the patch.

1. Use the workarounds.
2. Upgrade to the HP-UX 11i v2 September 2004 release
-> and install the patch.

TOUR(Transport Optional Upgrade Release) is available from

Workaround for CAN-2004-1060 may not be necessary.
Although changes in the binary files and patches for CAN-2004-0790
and CAN-2004-0791 do not prevent the exploit of CAN-2004-1060,
they do make it less likely to succeed. The sequence number check
suggested in section 5.1 of 'ICMP attacks against TCP' has been
implemented. The Internet Draft of 'ICMP attacks against TCP'
can be found here:
Customers should consider whether this check reduces the risk of
the exploit to the point that setting ip_pmtu_strategy=0 is not

->Note: ip_pmtu_strategy=0 sets the PMTU to 576 bytes.
-> For IPv4 the Next-Hop MTU may be as low as 68 bytes.
-> Therefore setting ip_pmtu_strategy=0 may cause
-> connections to stall.

If the workaround for CAN-2004-1060 is to be used, please note the
HPSBUX01137 recommends setting ip_pmtu_strategy = 0 or 3 as a
workaround for the problem of CAN-2005-1192. CAN-2004-1060 has a
different root cause and cannot be worked around with
p_pmtu_strategy=3. To work around both CAN-2005-1192 and
CAN-2004-1060 ip_pmtu_strategy=0 must be used.

Please refer to the Manual Actions section below for a summary of
the required actions.


CAN-2004-0790 and CAN-2004-0791

Filter out the following ICMP messages:

Type 3, Code 2 (Destination Unreachable, Protocol Unreachable)
Type 3, Code 3 (Destination Unreachable, Port Unreachable)
Type 4, Code 0 (Source Quench)


Set ip_pmtu_strategy=0.

Note: Filtering "Protocol Unreachable" and "Port Unreachable"
should not be done without careful testing. Filtering these
out may interfere with the correct functioning of network
components. Filtering "Source Quench" should present
little risk.

Setting ip_pmtu_strategy=0
Edit /etc/rc.config.d/nddconf to add the following:


where 'n' is the next available index value as described in the
nddconf comments.

This value will take effect when the system is rebooted.
Until the system can be rebooted use the following command
to read the /etc/rc.config.d/nddconf file and set the tunable

/usr/bin/ndd -c

The ip_pmtu_strategy parameter can be displayed by the following

/usr/bin/ndd -get /dev/ip ip_pmtu_strategy

Note: Since open connections will remain potentially vulnerable
until they are closed and certain internal data structures
are released it is recommended that the system be rebooted.

Note: There is a defect that will cause "ndd -c" to fail if there
are more than 10 directives in /etc/rc.config.d/nddconf.
That defect is fixed in the following patches:

B.11.11 - PHNE_25644 or subsequent
B.11.04 - PHNE_26076 or subsequent
B.11.00 - PHNE_26125 or subsequent

Preliminary binary files

->Preliminary binary files are available for B.11.22. Patches
are available for B.11.00, B.11.11 and B.11.23. The patches and
the preliminary binary files address CAN-2004-0790 and
CAN-2004-0791 only. Although changes in the patches and binary
files for CAN-2004-0790 and CAN-2004-0791 do not prevent the
exploit of CAN-2004-1060, they do make it less likely to succeed.

Instructions for downloading and installing the binary files are
contained in readme files available here:

System: hprc.external.hp.com (
Login: icmp
Password: icmp

FTP Access:
ftp://icmp:icmp (at) hprc.external.hp (dot) com [email concealed]/
or: ftp://icmp:icmp (at) 192.170.19 (dot) 51 [email concealed]/

Note: The links above may not work for all browsers. If the
link fails the url should be entered directly into the
browser's address field.

->Since a patch is available for B.11.00 the readme.11.00.txt and
corresponding binary files have been removed from the ftp site.

Since a patch is available for B.11.11 the readme.11.11.txt and
corresponding binary files have been removed from the ftp site.

Since a patch is available for B.11.23 the readme.11.23.txt and
corresponding binary files have been removed from the ftp site.

Download the appropriate readme file containing further


Verify the cksum or md5sum:

Note: The readme files have not changed since rev.1 of this
Security Bulletin.

cksum readme*
2836317466 2469 readme.11.22.txt

md5sum readme*
cafbb24f3dc7131501142f75deaeccbd readme.11.22.txt

Download and install the binary files as discussed in the readme
files. The binary files are available in the same directory as
the readme files.

1. Set ip_pmtu_strategy=0

a. Filter out the following ICMP messages:

Type 3, Code 2 (Destination Unreachable, Protocol Unreachable)
Type 3, Code 3 (Destination Unreachable, Port Unreachable)
Type 4, Code 0 (Source Quench)


b. Install the appropriate binary file or patch (binary file
not available for B.11.04).

Revision 0: 25 May 2005
Initial release

Revision 1: 1 June 2005
Binary files for B.11.00 and B.11.22 are available.
Added information about CAN-2004-1060.
The "set ip_pmtu_strategy=0" workaround is required even if
binary files are installed.
Removed IPSec information.

Revision 2: 19 June 2005
TOUR (Transport Optional Upgrade Release) on B.11.11 and B.11.23
is potentially vulnerable.
Added a description of the sequence number check implemented in
the binary files.

Revision 3: 27 June 2005
PHNE_33159 is available for B.11.11. The B.11.11 binary files
have been removed from the ftp site.

Revision 4: 10 July 2005
PHNE_32606 is available for B.11.23. The B.11.23 binary files
have been removed from the ftp site.

Revision 5: 24 July 2005
PHNE_33395 is available for B.11.00. The B.11.00 binary files
have been removed from the ftp site.
Added discussion of ip_pmtu_strategy=0. It is optional if
patches are installed.
Moved or deleted some text for readability.

HP-UX SPECIFIC SECURITY BULLETINS*: Security Patch Check revision
B.02.00 analyzes all HP-issued Security Bulletins to provide a
subset of recommended actions that potentially affect a specific
HP-UX system.

For more information:

SUPPORT: For further information, contact normal HP Services
support channel.

REPORT: To report a potential security vulnerability with any HP
supported product, send Email to: security-alert (at) hp (dot) com. [email concealed] It is
strongly recommended that security related information being
communicated to HP be encrypted using PGP, especially exploit
information. To obtain the security-alert PGP key please send an
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* The Software Product Category that this Security Bulletin
relates to is represented by the 5th and 6th characters of the
Bulletin number:
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System management and security procedures must be reviewed
frequently to maintain system integrity. HP is continually
reviewing and enhancing the security features of software products
to provide customers with current secure solutions.

"HP is broadly distributing this Security Bulletin in order to
bring to the attention of users of the affected HP products the
important security information contained in this Bulletin. HP
recommends that all users determine the applicability of this
information to their individual situations and take appropriate
action. HP does not warrant that this information is necessarily
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(c)Copyright 2005 Hewlett-Packard Development Company, L.P.
Hewlett-Packard Company shall not be liable for technical or
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The information in this document is subject to change without
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products referenced herein are trademarks of Hewlett-Packard
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Version: PGP 8.1


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