[security bulletin] SSRT5954 rev.0 HP-UX TCP/IP Remote Denial of Service (DoS)

Type securityvulns
Reporter Securityvulns
Modified 2005-04-26T00:00:00





SSRT5954 rev.0 - HP-UX TCP/IP Remote Denial of Service (DoS)

NOTICE: There are no restrictions for distribution of this Security Bulletin provided that it remains complete and intact.

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

INITIAL RELEASE: 24 April 2005

POTENTIAL SECURITY IMPACT: Remote Denial of Service (DoS)

SOURCE: Hewlett-Packard Company HP Software Security Response Team

VULNERABILITY SUMMARY: A potential security vulnerability has been identified with HP-UX running TCP/IP (IPv4). This vulnerability could be remotely exploited by an unauthorized user to cause a Denial of Service (DoS).


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 (IPv4).


 HP-UX B.11.23
 HP-UX B.11.22
 HP-UX B.11.11
 HP-UX B.11.04
 HP-UX B.11.00
 action: set ip_pmtu_strategy = 0 or 3


Certain network traffic can result in a Denial of Service (DoS) for HP-UX systems running TCP/IP (IPv4). Receiving a certain packet on any open TCP/IP connection can result in a Denial of Service (DoS) condition which can only be corrected by a reboot of the affected system.

Until patches are available to resolve the issue the Denial of Service (DoS) can be avoided by setting the ip_pmtu_strategy parameter to either 0 or 3.

Discussion of ip_pmtu_strategy

The default value for ip_pmtu_strategy is 1. This allows for PMTU discovery. Once the issue of this Security Bulletin has been resolved via patches the ip_pmtu_strategy value of 1 will again be the preferred setting for most situations.

The ip_pmtu_strategy values of 0 and 3 set the PMTU to a fixed size for destinations which are not on the local network.

The ip_pmtu_strategy value of 0 sets the PMTU to 576 bytes. Routers are required to handle packets of at least this size.

The ip_pmtu_strategy value of 3 sets the PMTU to 1500 bytes. This will generally result in more efficient transmission than the 576 byte PMTU. If it is known that the routers involved can handle a 1500 byte MTU the ip_pmtu_strategy value of 3 is preferred.

Patch requirements for setting ip_pmtu_strategy to 3

All affected HP-UX versions allow setting ip_pmtu_strategy to 0.

B.11.22 and B.11.23 have no patch requirements for setting ip_pmtu_strategy to 3.

B.11.11, B.11.04, and B.11.00 require the following patches in order to set ip_pmtu_strategy to 3:

B.11.11 - PHNE_25642 or subsequent B.11.04 - PHNE_26101 or subsequent B.11.00 - PHNE_25423 or subsequent

Reboot requirement for setting ip_pmtu_strategy

The ip_pmtu_strategy parameter can be set via the ndd(1M) command or by changing the nddconf file and rebooting the system. The ndd(1M) command only affects new connections. Existing connections will remain vulnerable until they terminate or until the system is rebooted and the nddconf value of ip_pmtu_strategy takes effect.

Note: It has been recommended in several places including HP-UX Bastille, System Health Check, and the Security Bulletin HPSBUX0001-110 that ip_pmtu_strategy be set to 1. This recommendation was made to avoid issues with which occurred when ip_pmtu_strategy was set to 2. The value 1 was recommended because it is the system default and for most situations results in the best performance. However, the values 0 and 3 also avoid the issues which occurred when ip_pmtu_strategy was set to 2. As mentioned above once the issue of this Security Bulletin has been resolved via patches the ip_pmtu_strategy setting of 1 will again be the preferred setting for most situations.

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

RESOLUTION: Until patches are available the Denial of Service (DoS) can be avoided by setting the ip_pmtu_strategy parameter to 0 or 3.

If the ip_pmtu_strategy value of 3 is desired for B.11.11, B11.04, or B.11.00 apply the patches listed in the Background section.

Edit /etc/rc.config.d/nddconf to add the following:

TRANSPORT_NAME[n]=ip NDD_NAME[n]=ip_pmtu_strategy NDD_VALUE[n]=0


TRANSPORT_NAME[n]=ip NDD_NAME[n]=ip_pmtu_strategy NDD_VALUE[n]=3

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

As discussed in the Background section the system must be rebooted for the new ip_pmtu_strategy to take effect.

Until the system can be rebooted the ip_pmtu_strategy value for new connections can be set with the ndd(1M) command:

/usr/bin/ndd -set /dev/ip ip_pmtu_strategy 0


/usr/bin/ndd -set /dev/ip ip_pmtu_strategy 3

MANUAL ACTIONS: Yes - NonUpdate set ip_pmtu_strategy = 0 or 3

BULLETIN REVISION HISTORY: Revision 0: 24 April 2005 Initial release

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: http://www.software.hp.com/cgi-bin/swdepot_parser.cgi/cgi/ displayProductInfo.pl?productNumber=B6834AA

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@hp.com. 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 e-mail message to security-alert@hp.com with the Subject of 'get key' (no quotes).

SUBSCRIBE: To initiate a subscription to receive future HP Security Bulletins via Email:

http://h30046.www3.hp.com/driverAlertProfile.php?regioncode=NA& langcode=USENG&jumpid=in_SC-GEN__driverITRC&topiccode=ITRC

On the web page: ITRC security bulletins and patch sign-up Under Step1: your IRTC security bulletins and patches - check ALL categories for which alerts are required and continue. Under Step2: your IRTC operating systems - verify your operating system selections are checked and save.

To update an existing subscription: http://h30046.www3.hp.com/subSignIn.php

Log in on the web page Subscriber's choice for Business: sign-in. On the Web page: Subscriber's Choice: your profile summary - use Edit Profile to update appropriate sections.

To review previously published Security Bulletins visit: http://itrc.hp.com/service/cki/secBullArchive.do

  • The Software Product Category that this Security Bulletin relates to is represented by the 5th and 6th characters of the Bulletin number: GN = HP General SW, MA = HP Management Agents, MI = Misc. 3rd party SW, MP = HP MPE/iX, NS = HP NonStop Servers, OV = HP OpenVMS, PI = HP Printing & Imaging, ST = HP Storage SW, TL = HP Trusted Linux, TU = HP Tru64 UNIX, UX = HP-UX, VV = HP Virtual Vault

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 accurate or complete for all user situations and, consequently, HP will not be responsible for any damages resulting from user's use or disregard of the information provided in this Bulletin. To the extent permitted by law, HP disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose, title and non-infringement."

(c)Copyright 2005 Hewlett-Packard Development Company, L.P. Hewlett-Packard Company shall not be liable for technical or editorial errors or omissions contained herein. The information provided is provided "as is" without warranty of any kind. To the extent permitted by law, neither HP nor its affiliates, subcontractors or suppliers will be liable for incidental, special or consequential damages including downtime cost; lost profits; damages relating to the procurement of substitute products or services; or damages for loss of data, or software restoration. The information in this document is subject to change without notice. Hewlett-Packard Company and the names of Hewlett-Packard products referenced herein are trademarks of Hewlett-Packard Company in the United States and other countries. Other product and company names mentioned herein may be trademarks of their respective owners.

-----BEGIN PGP SIGNATURE----- Version: PGP 8.1

iQA/AwUBQmzbKOAfOvwtKn1ZEQLMqgCg/VCdbSCfJGw4fKmii3EO9HS02rcAn0K0 3VwKveJSfeggNmrn09jHqoXV =PmY0 -----END PGP SIGNATURE-----