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 software updates that address this vulnerability.

  Workarounds that mitigate this vulnerability are available.

  This advisory is posted at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100721-spcdn.

Affected Products

• All versions of system software on the Cisco Internet Streamer application are vulnerable prior to the first fixed release.

  Vulnerable Products

  To determine the software version running on a Cisco Content Delivery Engine, log in to the device and issue the "show version" command line interface (CLI) command to display the system banner. Cisco CDS Internet Streamer software will identify itself as "Content Delivery System Software Release". On the same line of output, the version number will be provided. This example identifies a Cisco Content Delivery Engine that is running Cisco Content Delivery System software release 2.5.3:

  cdn-cde#show version
  Content Delivery System Software (CDS)
  Copyright ©) 1999-2010 by Cisco Systems, Inc.
  Content Delivery System Software Release 2.5.3 (build b8 Jan 21 2010)
  Version: cde200-2.5.3.8
  
  Compiled 16:07:11 Jan 21 2010 by ipvbuild
  Compile Time Options: KQ SS
  
  System was restarted on Thu Jun  3 04:09:25 2010.
  The system has been up for 2 hours, 11 minutes, 27 seconds.
  
  cdn-cde#

  Alternatively the Content Delivery System Manager home page gives a brief summary of the software versions in use on all the devices in the content delivery system network.

  To view the software version running on a particular device, choose Devices > Devices. The Devices Table page displays the software version for each device listed. For further information on finding the software version, refer to the "Maintaining the Internet Streamer CDS" at the following link: http://www.cisco.com/en/US/docs/video/cds/cda/is/2_5/configuration_guide/maint.html#wp1198510.

  Products Confirmed Not Vulnerable

  Cisco Content Delivery Engines running TV streaming content delivery applications and the Video Navigator Application are not affected.

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

Details

• 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.

Workarounds

• 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

Fixed Software

• 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

  Cisco Content Delivery System Software Release	First Fixed Release	Recommended Release
  2.2.x	Vulnerable, Migrate to 2.5.7 or later
  2.3.x	Vulnerable, Migrate to 2.5.7 or later
  2.4.x	Vulnerable, Migrate to 2.5.7 or later
  2.5.x	2.5.7	2.5.9

Exploitation and Public Announcements

• 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.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100721-spcdn

Revision History

• Revision 1.1	2010 July 29	Updated Details and Workaround sections
  Revision 1.0	2010 July 21	Initial public release

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