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Cisco Security Advisory

Cisco IOS Software SSL VPN Denial of Service Vulnerability

Advisory ID: cisco-sa-20140326-ios-sslvpn

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20140326-ios-sslvpn

Revision 1.0

For Public Release 2014 March 26 16:00  UTC (GMT)

Related Resources:

View related BlogView related Event ResponseView related Alert

Summary

A vulnerability in the Secure Sockets Layer (SSL) VPN subsystem of Cisco IOS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.

The vulnerability is due to a failure to process certain types of HTTP requests. To exploit the vulnerability, an attacker could submit crafted requests designed to consume memory to an affected device. An exploit could allow the attacker to consume and fragment memory on the affected device. This may cause reduced performance, a failure of certain processes, or a restart of the affected device.

Cisco has released free software updates that address this vulnerability. There are no workarounds to mitigate this vulnerability.

This advisory is available at the following link:
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20140326-ios-sslvpn

Note: The March 26, 2014, Cisco IOS Software Security Advisory bundled publication includes six Cisco Security Advisories. All advisories address vulnerabilities in Cisco IOS Software. Each Cisco IOS Software Security Advisory lists the Cisco IOS Software releases that correct the vulnerability or vulnerabilities detailed in the advisory as well as the Cisco IOS Software releases that correct all Cisco IOS Software vulnerabilities in the March 2014 bundled publication.

Individual publication links are in Cisco Event Response: Semiannual Cisco IOS Software Security Advisory Bundled Publication at the following link:

http://www.cisco.com/web/about/security/intelligence/Cisco_ERP_mar14.html

Affected Products

Vulnerable Products

Only devices that have been configured for the WebVPN Enhancements feature (Cisco IOS SSLVPN) are affected by this vulnerability.

To determine whether a device is enabled for WebVPN, the preferred method is to issue the show webvpn gateway EXEC command. A device is affected if it is running the vulnerable software and the configuration lists the Admin and Operation statuses of any configured gateway as up.

In the following example, the device has a single WebVPN gateway configured called ssl-vpn. The gateway is up and accepting connections
Router#show webvpn gateway

Gateway Name                       Admin  Operation
------------                       -----  ---------
ssl-vpn                            up     up
Administrators may also perform a configuration check by issuing the following EXEC commands, show running-config | include webvpn. If the device returns any output this means that SSLVPN is configured on the device and the device may be vulnerable. If the output from show running-config | include webvpn contains webvpn gateway <word>, then the device is configured to support the Cisco IOS SSLVPN feature. A device is vulnerable if it has the inservice command in at least one of the webvpn gateway sections. The following example shows a vulnerable device configured with Cisco IOS SSLVPN:
Router# show running-config | include webvpn
        
webvpn gateway ssl-vpn
 ip address 10.1.1.1 port 443  
 ssl trustpoint Gateway-TP
 inservice
 !
Router#
A device that supports the Cisco IOS SSLVPN is not vulnerable if it does not have a WebVPN gateway configured or all the configured WebVPN gateway entries contain the no inservice sub-command within the webvpn gateway section.

To determine the Cisco IOS Software release that is running on a Cisco product, administrators can log in to the device and issue the show version command to display the system banner. The system banner confirms that the device is running Cisco IOS Software by displaying text similar to "Cisco Internetwork Operating System Software" or "Cisco IOS Software." The image name displays in parentheses, followed by "Version" and the Cisco IOS Software release name. Other Cisco devices do not have the show version command or may provide different output.

The following example identifies a Cisco product that is running Cisco IOS Software Release 15.2(4)M5 with an installed image name of C3900-UNIVERSALK9-M:

Router> show version 
Cisco IOS Software, C3900 Software (C3900-UNIVERSALK9-M), 15.2(4)M5, RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2013 by Cisco Systems, Inc.
Compiled Fri 13-Sep-13 16:44 by prod_rel_team
!--- output truncated 

Additional information about Cisco IOS Software release naming conventions is available in White Paper: Cisco IOS and NX-OS Software Reference Guide.

Products Confirmed Not Vulnerable

Cisco IOS XE Software is not affected by this vulnerability.

Cisco IOS XR Software is not affected by this vulnerability.

Cisco ASA 5500 Series Adaptive Security Appliance is not affected by this vulnerability.

No other Cisco products are currently known to be affected by this vulnerability.

Details

Cisco IOS SSL VPN Denial of Service Vulnerability

A vulnerability in the Secure Sockets Layer (SSL) VPN subsystem of Cisco IOS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.

The vulnerability is due to a failure to process certain types of HTTP requests. To exploit the vulnerability, an attacker could submit crafted requests designed to consume memory to an affected device. An exploit could allow the attacker to consume and fragment memory on the affected device. This may cause reduced performance, a failure of certain processes, or a restart of the affected device.
A three-way TCP handshake must be completed for each malicious connection to an affected device; however, authentication is not required. The default TCP port number for SSLVPN is 443.
This vulnerability is documented in Cisco bug ID CSCuf51357 (registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2014-2112.

Vulnerability Scoring Details

Cisco has scored the vulnerability in this advisory based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this security advisory is in accordance with CVSS version 2.0.

CVSS is a standards-based scoring method that conveys vulnerability severity and helps organizations determine the urgency and priority of a response.

Cisco has provided a base and temporal score. Customers can also compute environmental scores that help determine the impact of the vulnerability in their own networks.

Cisco has provided additional information regarding CVSS at the following link:
http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html

Cisco has also provided a CVSS calculator to compute the environmental impact for individual networks at the following link:
http://intellishield.cisco.com/security/alertmanager/cvss


Cisco IOS SSL VPN Denial of Service Vulnerability - CSCuf51357

Calculate the environmental score of CSCuf51357

CVSS Base Score - 7.8

Access Vector

Access Complexity

Authentication

Confidentiality Impact

Integrity Impact

Availability Impact

Network

Low

None

None

None

Complete

CVSS Temporal Score - 6.4

Exploitability

Remediation Level

Report Confidence

Functional

Official-Fix

Confirmed


Impact

Successful exploitation of the vulnerability described in this document could allow an unauthenticated remote attacker to cause a DoS condition. This may take the form of either reduced performance of an affected device, a failure to maintain routing protocols, or a restart of the device.

Software Versions and Fixes

When considering software upgrades, customers are advised to consult the Cisco Security Advisories, Responses, and Notices archive at http://www.cisco.com/go/psirt and review subsequent advisories to determine exposure and a complete upgrade solution.

In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.

In February 2014, Cisco announced details of an industry-wide issue with memory components manufactured by a single supplier between 2005 and 2010. Although the majority of Cisco products that use these components are experiencing field failure rates below expected levels, a device reload or power cycle could expose component failures. While there are no known security implications associated with this issue, a subset of the affected products may experience a memory component failure during the software upgrade process. Cisco recommends customers review the related information and product-specific field notices at www.cisco.com/go/memory before making upgrade decisions. Each Field Notice indicates whether the product could experience the memory component failure during a software upgrade.

Cisco IOS Software

The Cisco IOS Software Checker is the quickest method to determine exposure to vulnerabilities in Cisco IOS Software. The tool allows customers to quickly identify Cisco Security Advisories that impact specific Cisco IOS Software releases. Users can initiate a search by selecting releases from the drop-down menu or uploading a file from their local system. The tool is also capable of parsing show version command output. Results can be customized by searching against all previously published Cisco Security Advisories, a specific publication, or all the advisories in the March 2014 Bundled Publication.

Customers can also use the Cisco IOS Software tables below to determine their exposure. Each row corresponds to a Cisco IOS Software release; if a particular release is vulnerable, the earliest releases that contain the fix are listed in the second column. The third column lists the earliest possible releases that correct all vulnerabilities in this Cisco IOS Software Security Advisory bundled publication.




Expand to View Detailed Fixed Software Information

Cisco IOS XE Software

Cisco IOS XE Software is not affected by the vulnerability documented in this advisory as part of the March 2014 Cisco IOS Software Security Advisory Bundled Publication.

Cisco IOS XR Software

Cisco IOS XR Software is not affected by any of the vulnerabilities that are disclosed in the March 2014 Cisco IOS Software Security Advisory Bundled Publication.

Workarounds

There are no workarounds for the vulnerability described in this Cisco Security Advisory.

Obtaining Fixed Software

Cisco has released free software updates that address the vulnerability described in this advisory. Prior to deploying software, customers are advised to consult their maintenance providers or check the software for feature set compatibility and known issues that are specific to their environments.

Customers may only install and expect support for feature sets they have purchased. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license at http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html.

Customers with Service Contracts

Customers with contracts should obtain upgraded software through their regular update channels. For most customers, upgrades should be obtained through the Software Navigator on Cisco.com at http://www.cisco.com/cisco/software/navigator.html.

Customers Using Third-Party Support Organizations

Customers with Cisco products that 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 organization for assistance with the appropriate course of action.

The effectiveness of any workaround or fix depends on specific customer situations, such as product mix, network topology, traffic behavior, and organizational mission. Because of the variety of affected products and releases, customers should consult their service providers or support organizations to ensure that any applied workaround or fix is the most appropriate in the intended network before it is deployed.

Customers Without Service Contracts

Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco Technical Assistance Center (TAC):
  • +1 800 553 2447 (toll free from within North America)
  • +1 408 526 7209 (toll call from anywhere in the world)
  • email: tac@cisco.com
Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade. Customers without service contracts should request free upgrades through the TAC.

Refer to Cisco Worldwide Contacts at http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html for additional TAC contact information, including localized telephone numbers, instructions, and email addresses for support in various languages.

Exploitation and Public Announcements

The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

This vulnerability was discovered by Cisco TAC during the investigation of customer cases.

Status of This Notice: Final

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.


Distribution

This advisory is posted on Cisco Security Intelligence Operations at the following link:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20140326-ios-sslvpn

Additionally, a text version of this advisory is clear signed with the Cisco PSIRT PGP key and circulated among the following email addresses:
  • cust-security-announce@cisco.com
  • first-bulletins@lists.first.org
  • bugtraq@securityfocus.com
  • vulnwatch@vulnwatch.org
  • cisco@spot.colorado.edu
  • cisco-nsp@puck.nether.net
  • full-disclosure@lists.grok.org.uk
Future updates of this advisory, if any, will reside on Cisco.com but may not be announced on mailing lists. Users can monitor this advisory's URL for any updates.

Revision History

Revision 1.0 2014-March-26 Initial public release.

Cisco Security Procedures

Complete information about reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco is available on Cisco.com at http://www.cisco.com/web/about/security/psirt/security_vulnerability_policy.html. This web page includes instructions for press inquiries regarding Cisco Security Advisories. All Cisco Security Advisories are available at http://www.cisco.com/go/psirt.
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