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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2009.1662 Vulnerability in Citrix NetScaler and Citrix Access Gateway Enterprise Edition Could Result in Denial of Service 18 December 2009 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Access Gateway 7.0 Enterprise Edition Access Gateway 8.0 Enterprise Edition Access Gateway 8.1 Enterprise Edition Access Gateway 9.0 Enterprise Edition Access Gateway 9.1 Enterprise Edition NetScaler Application Delivery Software 7.0 NetScaler Application Delivery Software 8.0 NetScaler Application Delivery Software 8.1 NetScaler Application Delivery Software 9.0 NetScaler Application Delivery Software 9.1 NetScaler VPX 9.1 Publisher: Citrix Operating System: Windows Impact/Access: Denial of Service -- Remote with User Interaction Resolution: Patch/Upgrade CVE Names: CVE-2008-4609 Reference: ESB-2009.1372 ESB-2009.1284 ESB-2009.1267.2 ESB-2009.1263 Original Bulletin: http://support.citrix.com/article/CTX123649 - --------------------------BEGIN INCLUDED TEXT-------------------- Vulnerability in Citrix NetScaler and Citrix Access Gateway Enterprise Edition Could Result in Denial of Service Document ID: CTX123649 / Created On: Dec 16, 2009 / Updated On: Dec 16, 2009 Average Rating: not yet rated Severity: Medium Description of Problem A vulnerability has been identified in the NetScaler and Access Gateway Enterprise Edition appliance firmware that could result in a limited denial of service. This vulnerability has been assigned the following CVE number(s): CVE CVE-2008-4609: The TCP implementation in (1) Linux, (2) platforms based on BSD Unix, (3) Microsoft Windows, (4) Cisco products, and probably other operating systems allows remote attackers to cause a denial of service (connection queue exhaustion) via multiple vectors that manipulate information in the TCP state table, as demonstrated by sockstress. This vulnerability is present in versions of all versions of Citrix NetScaler and Citrix Access Gateway Enterprise Edition up to and including version 9.1. Mitigating Factors In order to sustain this denial of service, the attacker would have to maintain a high volume of traffic against the target appliance. What Customers Should Do This vulnerability has been addressed in versions 9.1.100.3 and 8.1.68.7 of the firmware for Citrix NetScaler and Access Gateway Enterprise Edition. Citrix recommends that customers upgrade their NetScaler and Access Gateway Enterprise Edition appliances to these builds of the versions 8.1 and 9.1 firmware, available at the following locations: Citrix NetScaler: http://www.citrix.com/English/ss/downloads/results.asp?productID=21679 Citrix Access Gateway Enterprise Edition: http://www.citrix.com/English/ss/downloads/results.asp?productID=15005&c1=pov1680613 Customers using versions of the NetScaler and Access Gateway Enterprise Edition firmware that do not currently have a fix available are recommended to implement the following mitigations: NetScaler/Access Gateway Enterprise Edition 9.0/9.1 - From the NSCLI, 1. Ensure that the limited persist probe is enabled. The setting is enabled by default, but can be verified using the following command: > show ns tcpparam If the probe is not enabled, it can be enabled using the following command: > set tcpparam limitedPersist ENABLED 2. Modify the client idle timeout value for an existing vServer or service to a lower value, e.g. 60 seconds, using the following command: > Set lb vserver <vsvrname> -clttimeout 60 3. Modify the global client idle timeout value to a lower value, e.g. 60 seconds, using the following command: For TCP vServers > set ns timeout -tcpclient 60 For HTTP vServers > set ns timeout -httpclient 60 NetScaler/Access Gateway Enterprise Edition 8.1 - From the shell, 1. Ensure that the limited persist probe is enabled. The setting is enabled by default, but can be verified and enabled using the following command: bash# nsapimgr -ys limited_persistprobe=1 - From the NSCLI, 1. Modify the client idle timeout value for an existing vServer or service to a lower value, e.g. 60 seconds, using the following command: > Set lb vserver <vsvrname> -clttimeout 60 2. Modify the global client idle timeout value to a lower value, e.g. 60 seconds, using the following command: > set ns timeout -client 60 NetScaler/Access Gateway Enterprise Edition 8.0 - From the shell, 1. Ensure that the limited persist probe is enabled. The setting is enabled by default, but can be verified and enabled using the following command: bash# nsapimgr -ys limited_persistprobe=1 - From the NSCLI, 2. Modify the client idle timeout value for an existing vServer or service to a lower value, e.g. 60 seconds, using the following command: > Set lb vserver <vsvrname> -clttimeout 60 3. Modify the global client idle timeout value to a lower value, e.g. 60 seconds, using the following command: > set ns idletimeout tcpclt 60 NetScaler 7.0 - From the shell, 1. Ensure that the limited persist probe is enabled. The setting is enabled by default, but can be verified and enabled using the following command: bash# nsapimgr -ys limited_persistprobe=1 - From the NSCLI, 2. Modify the client idle timeout value for an existing vServer or service to a lower value, e.g. 60 seconds, using the following command: > Set lb vserver <vsvrname> -clttimeout 60 - From the shell, 3. Modify the global client idle timeout value to a lower value, e.g. 60 seconds, using the following command: bash# nsapimgr ys clientconnidletimeout=6000 Note that this timeout value increments in 10ms intervals. Citrix recommends that thorough testing is carried out on any NetScaler or Access Gateway Enterprise Edition appliance that has been modified in this way prior to deployment in a live environment. What Citrix Is Doing Citrix is notifying customers and channel partners about this potential security issue. This article is also available from the Citrix Knowledge Center at http://support.citrix.com/. Obtaining Support on This Issue If you require technical assistance with this issue, please contact Citrix Technical Support. Contact details for Citrix Technical Support are available at http://www.citrix.com/site/ss/supportContacts.asp. Reporting Security Vulnerabilities to Citrix Citrix welcomes input regarding the security of its products and considers any and all potential vulnerabilities seriously. If you would like to report a security issue to Citrix, please compose an e-mail to secure@citrix.com stating the exact version of the product in which the vulnerability was found and the steps needed to reproduce the vulnerability This document applies to: * Access Gateway 7.0 Enterprise Edition * Access Gateway 8.0 Enterprise Edition * Access Gateway 8.1 Enterprise Edition * Access Gateway 9.0 Enterprise Edition * Access Gateway 9.1 Enterprise Edition * NetScaler Application Delivery Software 7.0 * NetScaler Application Delivery Software 8.0 * NetScaler Application Delivery Software 8.1 * NetScaler Application Delivery Software 9.0 * NetScaler Application Delivery Software 9.1 * NetScaler VPX 9.1 - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. 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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 iD8DBQFLKwNONVH5XJJInbgRAi0AAKCLE3My3hJX4Z0nXR+DoPnNZbPqwgCeP/eS 7yiIz2HzYD4XuiZiv0sa6Ck= =2cyW -----END PGP SIGNATURE-----