Summary

• Cisco CNS Network Registrar Domain Name Service /Dynamic Host Configuration Protocol (DNS/DHCP) server for the Windows Server platforms is vulnerable to a Denial of Service attack when a certain crafted packet sequence is directed to the server. Cisco has made free software available to address this vulnerability for all affected customers.

  The vulnerabilities are documented as the following Cisco Bug IDs: CSCeg27625 and CSCeg27614.

  This advisory will be posted at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20041202-cnr.

Affected Products

• This section provides details on affected products.

  Vulnerable Products

  Cisco CNS Network Registrar for Windows NT server and Windows 2000

  Two issues are described in this advisory CSCeg27625 and CSCeg27614. Cisco CNS Network Registrar version 6.0 through 6.1.1.3 are affected by CSCeg27625. However, all versions up to and including version 6.1.1.3 are also affected by CSCeg27614.

  Products Confirmed Not Vulnerable

  The following Cisco Network Registrar products are not vulnerable to the issues described in this advisory:

  • Cisco Network Registrar for Unix
    
  • Cisco Network Registrar for Linux
    

  No other Cisco products are currently known to be affected by these vulnerabilities.

Details

• Cisco CNS Network Registrar is a DNS and DHCP server installed on Windows NT servers and Windows 2000 servers. Two separate vulnerabilities may impact system stability or availability if exploited. These issues are detailed below:

  • CSCeg27625 —The Cisco CNS Network Registrar CCM (Central Configuration Management) server may consume almost 100% of the system CPU when a remote user ends a connection after sending a specific sequence of packets. The server agent must be restarted to clear this condition.
    
  • CSCeg27614 —The Cisco CNS Network Registrar lock manager process may crash when the system receives an unexpected packet sequence. This will cause the CCM server to also fail. You must restart the server agent to resume normal operations.
    

  These issues are unrelated to the recent Cisco Security Advisory regarding Cisco IOS DHCP implementation. https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20041110-dhcp These issues are also unrelated to the recent UNIRAS advisory regarding DNS.

Workarounds

• These vulnerabilities can be mitigated by placing access lists on adjacent network devices such as routers or firewalls to block inbound connections to all high or ephemeral port numbers, including the CCM port.

  If remote access to the Cisco CNS Network Registrar is required, it is recommended that trusted hosts be explicitly permitted in access control lists, and all other connection attempts blocked. Remote connection CLI ports are tcp 2785 & tcp 2786, and the default port number for CCM is tcp1234, which can also be configured to a different port number. Access lists permitting selective access to these ports from trusted IP addresses can mitigate this vulnerability.

  The effectiveness of any workaround 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 is the most appropriate for use in the intended network before it is deployed.

Fixed Software

• The two issues are fixed in the 6.1.1.4 patch release. Releases are available for download to registered customers on CCO at: http://www.cisco.com/pcgi-bin/Software/Tablebuild/tablebuild.pl/nr-eval

  Customers who are using Cisco Network Registrar 5.5 versions must request a new license key for the Cisco CNS Network Registrar 6.1.1.x release before obtaining the patched 6.1.1.4 release from CCO. Version 5.5 license keys are incompatible with the Cisco CNS Network Registrar 6.0 or 6.1 software releases. To request a new license key, any customer wishing to upgrade version 5.5 to version 6.1 software should send an electronic mail message to cnr-psirt-update@cisco.com, and provide the customer name, address, contact name and existing version 5.5 license key string in the body of the message along with a line indicating ‘CNR PSIRT upgrade for Windows request’. A new license key will be dispatched via email to the requestor, allowing them to install and upgrade to the patched 6.1.1.4 release using the new license key.

  When considering software upgrades, please also consult http://www.cisco.com/en/US/products/products_security_advisories_listing.html 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”) for assistance. TAC contacts are as follows.

  • +1 800 553 2447 (toll free from within North America)
    
  • +1 408 526 7209 (toll call from anywhere in the world)
    
  • e-mail: tac@cisco.com
    

Exploitation and Public Announcements

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

  The discovery and documentation of this vulnerability was conducted by the Qualys Security Research Team. More information about the Qualys Security Research Team can be found at their website: http://www.qualys.com

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20041202-cnr

Revision History

• Revision 1.1	2004-December-07	Corrected transposed digits in workaround section of port numbers 2875 to 2785 and 2876 to 2786.
  Revision 1.0	2004-December-02	Initial public release.

  Show Less