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Category:   Device (Router/Bridge/Hub)  >   HPE ProCurve Switch Vendors:   HPE
(HP Issues Recommendation For ProCurve Switches) Multiple Vendor TCP Stack Implementations Let Remote Users Deny Service
SecurityTracker Alert ID:  1010216
SecurityTracker URL:
CVE Reference:   CVE-2004-0230   (Links to External Site)
Date:  May 19 2004
Impact:   Denial of service via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): HP ProCurve Routing Switch 9315M, 9308M, and 9304M
Description:   A vulnerability was reported in several TCP stack implementations. A remote user may be able to cause denial of service conditions using a TCP reset attack. HP's ProCurve switches are affected.

The UK National Infrastructure Security Co-Ordination Centre (NISCC) reported that some implementations of the Transmission Control Protocol (TCP) are particularly vulnerable to TCP reset attacks. A remote user can cause TCP sessions to terminate prematurely, causing denial of service conditions.

The specific impact on applications that use TCP depends on the mechanisms built into the application to address premature TCP session termination.

According to the report, NISCC considers the Border Gateway Protocol (BGP) to be one of the most affected applications, as it relies on a persistent TCP session between BGP peer entities. Premature termination of an underlying TCP session may require routing tables to be rebuilt and may cause "route flapping". In the case of BGP, using the TCP MD5 Signature Option and anti-spoofing measures can mitigate the vulnerability.

Other applications, such as Domain Name System (DNS) and (Secure Sockets Layer) SSL based applications may also be affected, but to a lesser degree, the report said.

A remote user can reportedly send a TCP packet with the RST (reset) flag set (or the SYN flag) with the appropriate spoofed source and destination IP addresses and TCP ports to cause the TCP session to be terminated. Ordinarily, the remote user may have the probability of 1 in 2^32 of guessing the correct sequence number, the report said. However, in actuality, a remote user may be able to guess an appropriate sequence number with much greater probability because many implementations will accept any sequence number within a certain window of the expected sequence number. The Associate Press reports that the proper number can be guessed within as few as four attempts, requiring only seconds to achieve.

The report credits Paul A. Watson for discovering a practical method for conducting TCP reset attacks (presented in "Slipping In The Window: TCP Reset Attacks" at the CanSecWest 2004 conference).

The report indicates that the following vendors are affected [this is not an inclusive list]:

- Cray Inc. is vulnerable on their UNICOS, UNICOS/mk and UNICOS/mp systems

- Check Point is affected, but has issued a protection mechanism in the latest release for VPN-1/FireWall-1 (R55 HFA-03) that can protect both the firewall device and hosts located behind the firewall.

- Internet Initiative Japan, Inc (IIJ) is affected.

- InterNiche NicheStack and NicheLite are affected.

- Juniper Networks products are affected.

- Cisco products are affected, including IOS and non-IOS based devices.

Other vendors are assessing the impact of this flaw.

The NISCC Vulnerability Advisory 236929 is available at:

Impact:   A remote user can cause denial of service on the target TCP session. The specific impact depends on the specific vendor implementation.
Solution:   For the HP ProCurve Routing Switch 9315M, 9308M, and 9304M, HP recommends that customers using BGP implement the MD5 has protection as soon as possible.
Cause:   State error

Message History:   This archive entry is a follow-up to the message listed below.
Apr 20 2004 Multiple Vendor TCP Stack Implementations Let Remote Users Deny Service

 Source Message Contents

Subject:  SSRT4696 rev.0 HP ProCurve Routing Switches TCP Denial of Service



SSRT4696 rev.0 HP ProCurve Routing Switches TCP Denial of Service (DoS)


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

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

18 May 2004


Denial of Service (DoS)

HP Software Security Response Team

NISCC 236929, CAN-2004-0230, TA04-111A
A potential security vulnerability has been identified with HP ProCurve Routing Switches 
running TCP where the vulnerability  could be exploited remotely to create a Denial of 
Service (DoS).
SUPPORTED SOFTWARE VERSIONS*:  ONLY impacted versions are listed.
HP ProCurve Routing Switch 9315M, 9308M, and 9304M and all managed HP EtherTwist, HP 
AdvanceStack and HP ProCurve devices.
This information is applicable for the following security vulnerability alerts:

NISCC Vulnerability Advisory 236929 - Vulnerability Issues in TCP

US-CERT Technical Cyber Security Alert TA04-111A Vulnerabilities in TCP

CVE name CAN-2004-0230

The industry standard TCP specification (RFC793) has a vulnerability whereby established 
TCP connections can be reset by an attacker.  The TCP stack that is part of the software 
used in managed HP EtherTwist, HP AdvanceStack and HP ProCurve devices is in conformance 
with this specification, and therefore contains this potential vulnerability.  The TCP 
connections that are affected due to this situation are only those terminating on these 
devices, not those passing through these devices.

HP ProCurve Routing Switch 9315M, 9308M, and 9304M which have BGP functionality can 
experience a Denial of Service, the duration of which would be the time needed by the 
device to rebuild routing tables.

TCP sessions, including Telnet, SSH, SFTP and HTTP on all managed HP EtherTwist, HP 
AdvanceStack and HP ProCurve devices may be disconnected without warning. TCP sessions 
that have been disconnected can be re-established.
For the HP ProCurve Routing Switch 9315M, 9308M, and 9304M, the BGP technology can be 
protected by using the MD5 hash protection feature.  HP recommends that our BGP customers 
implement MD5 protection as soon as possible to protect their connections against this 
type of attack.

Other managed HP EtherTwist, HP AdvanceStack and HP ProCurve devices are generally not 
impacted as TCP sessions that were disconnected can be re-established.

As a good practice, HP recommends the appropriate inactivity timeout feature on the device 
for each type of TCP session be implemented. TCP sessions include Telnet, SSH, SFTP and HTTP.
Please write to to request a PGP signed version of this bulletin.

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

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

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Complete the form and Save.

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system alerts will only receive one copy of all the non-operating system alerts).

REPORT: To report a potential security vulnerability with any HP supported product, send 
Email to: 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 with the Subject of 'get key' (no quotes).

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."

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 or 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.


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