Summary
Affected Products
Details
Vulnerability Scoring Details
Impact
Software Versions and Fixes
Workarounds
Obtaining Fixed Software
Exploitation and Public Announcements
Status of this Notice: FINAL
Distribution
Revision History
Cisco Security Procedures
The Cisco Application Control Engine Global Site Selector (GSS) contains a vulnerability when processing specific Domain Name System (DNS) requests that may lead to a crash of the DNS service on the GSS.
Cisco has released free software updates that address this vulnerability.
A workaround that mitigates this vulnerability is available.
This advisory is posted at http://www.cisco.com/warp/public/707/cisco-sa-20090107-gss.shtml.
All versions of GSS system software prior to 3.0(1) are affected by this vulnerability. If the GSS is configured with the optional Cisco Network Registrar (CNR) software, the device is not vulnerable.
The following GSS products are affected by this vulnerability:
In order to determine the software that runs on a GSS device, users should log in to the device and issue the show version command to display the system software banner. The version is indicated on the line starting with Version. The following example shows a GSS that runs system software 2.0(1):
gss.cisco.com#show version Global Site Selector (GSS) Model Number: GSS-4491-k9 Copyright (c) 1999-2007 by Cisco Systems, Inc. Version 2.0(1) Uptime: 19 Hours 18 Minutes and 14 seconds gss.cisco.com#
In order to determine if CNR is enabled on the GSS device, users should log in to the device and issue the show running-config | grep cnr command to display the system CNR configuration. If CNR is enabled, cnr enable will be displayed in the output. If CNR is disabled, no cnr enable will be displayed. The following example shows a GSS that does not have CNR enabled:
GSS.cisco.com#show running-config | grep cnr no cnr enable GSS.cisco.com#
The following products have been confirmed not vulnerable:
No other Cisco products are currently known to be affected by this vulnerability.
The Cisco GSS platform allows customers to leverage global content deployment across multiple distributed and mirrored data locations, optimizing site selection, improving Domain Name System (DNS) responsiveness, and ensuring data center availability.
The GSS is inserted into the traditional DNS hierarchy and is closely integrated with the Cisco CSS, Cisco Content Switching Module (CSM), or third-party server load balancers (SLBs) to monitor the health and load of the SLBs in customers data centers. The GSS uses this information and user-specified routing algorithms to select the best-suited and least-loaded data center in real time.
A vulnerability exists in the GSS when processing a specific sequence of DNS requests. An exploit of the vulnerability may result in a crash of the DNS service on the GSS.
When the DNS server crashes, an error message will appear in the logs similar to the following example:
Dec 18 04:47:21 gss NMR-6-LAUNCHSVR_EXIT[27261] dnsserver' has exited [ExitUnknown(139)]"
This vulnerability is documented in Cisco Bug ID: CSCsj70093 ( registered customers only)
This vulnerability has been assigned the Common Vulnerabilities and Exposures (CVE) identifier CVE-2008-3819.
Cisco has provided scores for the vulnerabilities in this advisory based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this Security Advisory is done in accordance with CVSS version 2.0.
CVSS is a standards-based scoring method that conveys vulnerability severity and helps determine urgency and priority of response.
Cisco has provided a base and temporal score. Customers can then compute environmental scores to assist in determining the impact of the vulnerability in individual networks.
Cisco has provided an FAQ to answer additional questions regarding CVSS at
http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html .
Cisco has also provided a CVSS calculator to help compute the environmental impact for individual networks at
http://intellishield.cisco.com/security/alertmanager/cvss .
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CSCsj70093: GSS DNS service may crash when processing specific DNS requests. Calculate the environmental score of CSCsj70093 |
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CVSS Base Score - 7.8 |
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Access Vector |
Access Complexity |
Authentication |
Confidentiality Impact |
Integrity Impact |
Availability Impact |
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Network |
Low |
None |
None |
None |
Complete |
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CVSS Temporal Score - 6.4 |
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Exploitability |
Remediation Level |
Report Confidence |
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Functional |
Official-Fix |
Confirmed |
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Successful exploitation of the vulnerability may result in a crash of the GSS DNS service. Repeated exploitation may result in a sustained denial of service (DoS) attack.
When considering software upgrades, also consult http://www.cisco.com/go/psirt and any subsequent advisories to determine exposure and a complete upgrade solution.
In all cases, customers should exercise caution to be certain the devices to be upgraded contain sufficient memory and that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, contact the Cisco Technical Assistance Center (TAC) or your contracted maintenance provider for assistance.
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GSS Major Version |
First Fixed Release |
Recommended Release |
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1.x(y) |
Vulnerable; Option1: Migrate to 3.0(1) or later; Option 2: Migrate to 2.0(5) or later. |
3.0(2) |
|
2.x(y) |
Vulnerable; Migrate to 2.0(5) or later; |
3.0(2) |
|
3.x(y) |
Not Vulnerable |
GSS fixed system software is available for download from http://www.cisco.com/pcgi-bin/tablebuild.pl/gss-3des?psrtdcat20e2
A workaround for this vulnerability requires the administrator to disable the property "ServerConfig.dnsserver.returnError" ( set to zero). On GSS version 1.1(x), 1.2(x) and 1.3(x), this property is disabled by default.
On GSS version 2.0(x), this property is enabled by default (set to one).
The following example shows how to disable this property:
GSS#config terminal
GSS(config)#property set ServerConfig.dnsserver.returnError 0
GSS(config)#exit
GSS#write memory
To ensure the workaround has been applied properly, from privileged exec mode, execute the show properties command and verify that the response returned shows "ServerConfig.dnsserver.returnError" parameter set to zero. The following example shows how to verify the workaround has been sucessfully applied:
gss.cisco.com#show properties | grep ServerConfig.dnsserver.returnError
ServerConfig.dnsserver.returnError : 0
For the property to take affect, the GSS should be stopped and restarted:
GSS#gss stop
GSS#gss start
Note:
If there is a query for which there is no domain match on the GSS, such a query is dropped and the DNSQueriesUnmatched counter is incremented. As a side-effect of the workaround, neither of the negative responses NXDOMAIN,NODATA are sent for queries for which there is no domain match.
Cisco has released free software updates that address these vulnerabilities. Prior to deploying software, customers should consult their maintenance provider or check the software for feature set compatibility and known issues specific to their environment.
Customers may only install and expect support for the feature sets they have purchased. By installing, downloading, accessing or otherwise using such software upgrades, customers agree to be bound by the terms of Cisco's software license terms found at http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html, or as otherwise set forth at Cisco.com Downloads at http://www.cisco.com/public/sw-center/sw-usingswc.shtml.
Do not contact psirt@cisco.com or security-alert@cisco.com for software upgrades.
Customers with contracts should obtain upgraded software through their regular update channels. For most customers, this means that upgrades should be obtained through the Software Center on Cisco's worldwide website at http://www.cisco.com.
Customers whose Cisco products are provided or maintained through prior or existing agreements with third-party support organizations, such as Cisco Partners, authorized resellers, or service providers should contact that support organization for guidance and assistance with the appropriate course of action in regards to this advisory.
The effectiveness of any workaround or fix is dependent on specific customer situations, such as product mix, network topology, traffic behavior, and organizational mission. Due to the variety of affected products and releases, customers should consult with their service provider or support organization to ensure any applied workaround or fix is the most appropriate for use in the intended network before it is deployed.
Customers who purchase direct from Cisco but do not hold a Cisco service contract, and customers who purchase through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should acquire upgrades by contacting the Cisco Technical Assistance Center (TAC). TAC contacts are as follows.
Customers should have their product serial number available and be prepared to give the URL of this notice as evidence of entitlement to a free upgrade. Free upgrades for non-contract customers must be requested through the TAC.
Refer to http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html for additional TAC contact information, including localized telephone numbers, and instructions and e-mail addresses for use in various languages.
The Cisco PSIRT is aware of active exploitations where malicious use of the vulnerability described in this advisory has occurred.
This vulnerability was discovered by investigating customer TAC service requests.
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.
This advisory is posted on Cisco's worldwide website at :
http://www.cisco.com/warp/public/707/cisco-sa-20090107-gss.shtml
In addition to worldwide web posting, a text version of this notice is clear-signed with the Cisco PSIRT PGP key and is posted to the following e-mail and Usenet news recipients.
Future updates of this advisory, if any, will be placed on Cisco's worldwide website, but may or may not be actively announced on mailing lists or newsgroups. Users concerned about this problem are encouraged to check the above URL for any updates.
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Revision 1.1 |
2009-November-12 |
Updated workarounds |
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Revision 1.0 |
2009-January-07 |
Initial public release |
Complete information on reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco, is available on Cisco's worldwide website at http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html. This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at http://www.cisco.com/go/psirt.
| Updated: Nov 12, 2009 | Document ID: 109384 |