Cisco Security Advisory

Advisory ID: cisco-sa-20100721-spcdn

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100721-spcdn

Revision 1.1

For Public Release 2010 July 21 16:00  UTC (GMT)

Summary

The Cisco Internet Streamer application, part of the Cisco Content Delivery System, contains a directory traversal vulnerability on its web server component that allows for arbitrary file access. By exploiting this vulnerability, an attacker may be able to read arbitrary files on the device, outside of the web server document directory, by using a specially crafted URL.

An unauthenticated attacker may be able to exploit this issue to access sensitive information, including the password files and system logs, which could be leveraged to launch subsequent attacks.

Cisco has released free software updates that address this vulnerability.

Workarounds that mitigate this vulnerability are available.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100721-spcdn.

Affected Products

The Cisco Internet Streamer application provides edge caching, content streaming, and downloads to subscriber IP devices such as PCs.

The Cisco Internet Streamer application, part of the Cisco Content Delivery System, contains a directory traversal vulnerability on its web server component that allows for arbitrary file access. It is possible to read arbitrary files on the Cisco Content Delivery Engine running the internet streamer application outside the web server's document directory using a specially-crafted URL. This includes the password files used to hold admin account details and system logs.

An unauthenticated attacker may be able to exploit this issue to access sensitive information that could be leveraged to launch subsequent attacks.

On the Service Engine and the Cisco Content Delivery System Manager this vulnerability can be exploited over all open HTTP ports; TCP ports 80 (Default HTTP port), 443 (Default HTTPS port) and 8090 (Alternate HTTP and HTTPS port), as well as those that are configured as part of the HTTP proxy.

On the Service Router this issue is seen on port TCP port 8090 (Alternate HTTP and HTTPS port).

In Cisco content delivery system software 2.5.3 and earlier, it is possible to configure "Enable Incoming Proxy", which when enabled, accepts incoming requests on configured ports, in addition to TCP port 80. The additional ports that the device will listen on for HTTP requests is defined in the "List of Incoming HTTP Ports" field, within "Devices > Devices > Application Control > Web > HTTP > HTTP Connections" of the content delivery system manager menu. For further information on HTTP settings, refer to the "Cisco Internet Streamer CDS 2.5 Software Configuration Guide - Configuring Devices" at the following link: http://www.cisco.com/en/US/docs/video/cds/cda/is/2_5/configuration_guide/configdevice.html.

This vulnerability is documented in the Cisco Bug ID CSCtd68063 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2010-1577.

Cisco has provided scores for the vulnerability 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 .

An unauthenticated attacker may be able to exploit this issue to access sensitive information, including the password files and system logs, which could be leveraged to launch subsequent attacks.

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.

The recommended release contains other software fixes that are recommended by Cisco. For further information please consult the release notes at the following link: http://www.cisco.com/en/US/docs/video/cds/cda/is/2_5/release_notes/CDS_RelNotes2_5_9.html#wp100128

As an interim step prior to upgrading the Cisco content delivery system software, it is possible to deny access to sensitive directories via service rules. This workaround is applicable to the Service Engine only. The following example shows denying access to move up a directory level. This also caters for other directory moves, such as "\.\./", ".\./" or "\../":

rule enable
rule action block pattern-list 1
rule pattern-list 1 url-regex ^http://.*/../.* 
rule pattern-list 1 url-regex ^https://.*/../.*

For more information on configuring service rules and for instructions on how to perform this via the content delivery system manager, consult the Cisco Internet Streamer CDS 2.5 Software Configuration Guide at the following link: http://www.cisco.com/en/US/docs/video/cds/cda/is/2_5/configuration_guide/configdevice.html#wp1773573.

Cisco CDS Engine IP Access Control Lists

This workaround is applicable only for the service router and Content Delivery System Manager, which do not have support for the above service rules. It is not applicable to the service engine.

Although it is often difficult to block traffic that transits a network, it is possible to identify traffic that should never be allowed to target infrastructure devices and block that traffic at the interface of the device or at the border of networks. The IP ACL example below provides an example of a trusted network segment 192.168.10.X that is allowed HTTP access (on TCP ports 80 and 443) to the Cisco content delivery service engine interface IP address 10.1.1.1. All other HTTP traffic to this address is dropped.

Note: The IP ACL should include all the configured interface IP addresses on the Cisco content delivery service engine. In this example only one interface IP address is shown:

ip access-list extended cisco-sa-20100721-spcdn
     permit tcp 192.168.10.0 0.0.0.255 host 10.1.1.1 eq www
     permit tcp 192.168.10.0 0.0.0.255 host 10.1.1.1 eq https
    

    !--
    !-- TCP port 8090 is not normally used so normally will not have to
    !-- be explicitly permitted. 
    !--
    !-- Permit any additional TCP ports that may have been configured
    !-- via the HTTP Proxy before continuing to add the deny statements.
    !--

     deny tcp any host 10.1.1.1 eq 8090
     deny tcp any host 10.1.1.1 eq www
     deny tcp any host 10.1.1.1 eq https
     permit ip any any
     exit

Apply the IP ACL to all interfaces on the Cisco content delivery service router or Content Delivery System Manager. In this example only one interface is shown:

interface GigabitEthernet 2/0
     ip address 10.1.1.1 255.255.255.0
     ip access-group cisco-sa-20100721-spcdn in

For more information on configuring IP access-lists and for instructions on how to perform this via the content delivery system manager, consult the Cisco Internet Streamer CDS 2.5 Software Configuration Guide at the following link: http://www.cisco.com/en/US/docs/video/cds/cda/is/2_5/configuration_guide/configdevice.html#wp1086184

Cisco has released free software updates that address this vulnerability. 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 Service Contracts

Customers Using Third-Party Support Organizations

Customers Without Service Contracts

The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory.

This vulnerability was reported to Cisco by BT and identified by Christopher Richardson & Simon John.

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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100721-spcdn

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.

• 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
  
• comp.dcom.sys.cisco@newsgate.cisco.com
  

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.

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.