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Cisco Security Advisory

VCO/4K Remote Password Disclosure

Advisory ID: cisco-sa-20001026-vco4k-password

Revision 1.0

For Public Release 2000 October 26 22:00  UTC (GMT)


A vulnerability in the Cisco VCO/4K exposes the passwords of authorized users in an easily decrypted format in response to a read-only SNMP query.

All currently supported releases prior to VCO/4K software version 5.1.4 are vulnerable to this defect. Version 5.1.4, currently available, contains a fix that prevents the display of the weakly encrypted passwords. Version 5.2, to become available in early December 2000, includes that fix as well as multiple improvements to password encryption and handling.

Free software upgrades are offered to all affected VCO/4K customers. The defect can be worked around by limiting access to the SNMP service on the VCO/4K.

This vulnerability is documented as Cisco Bug ID CSCds55790.

No other Cisco product is affected by this vulnerability.

This advisory is available at .

Affected Products

This section provides details on affected products.

Vulnerable Products

All currently supported releases prior to software version 5.1.4 for the Cisco VCO/4K are vulnerable due to this defect. Version 5.1.4 was released to customers in mid-August 2000.

Products Confirmed Not Vulnerable

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


The Cisco VCO/4K (Virtual Central Office 4000) is a programmable switch that provides voice services such as integrated messaging, operates as a core infrastructure switch for wireline or wireless networks, or acts as a gateway in mixed circuit- and packet-switched networks. The VCO/4K was developed by Summa Four, which was acquired by Cisco Systems in November 1998.

The usernames and encrypted passwords on the VCO/4K can be displayed remotely in response to an SNMP (Simple Network Management Protocol) query over the network. However, the passwords are encrypted using a substitution cipher that can be easily decrypted. This defect is documented as Cisco Bug ID CSCds55790.

The VCO/4K software has been patched to prevent the retrieval of the usernames and encrypted passwords via SNMP queries, and the password encryption has been replaced with the "Type 5" password encryption available in Cisco IOS software. Type 5 passwords are based on MD5, a secure one-way hash, and are considerably more resilient to unauthorized disclosure than a substitution cipher. In addition, the newer password encryption has been applied to multiple forms of access to the VCO/4K, and access control to the system has been improved in general.

Vulnerability Scoring Details

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 .

Cisco has also provided a CVSS calculator to help compute the environmental impact for individual networks at .


This vulnerability may be exploited to gain unauthorized control of an affected VCO/4K system. The usernames and passwords are available to anyone who can perform an SNMP query to the VCO/4K and receive the response, or can obtain the usernames and encrypted passwords using other means. The older encryption method provides minimal protection for the passwords, and can be trivially decrypted by an attacker to gain complete management control of the VCO/4K system.

Software Versions and Fixes

Cisco VCO/4K software version 5.1.4 contains a partial fix in which the encrypted passwords are no longer returned in response to a SNMP query. This version became available in mid-August 2000.

Version 5.2, scheduled for release 2000-12-04, continues to prevent passwords from unauthorized disclosure via SNMP, and contains improvements to VCO/4K password encryption processing equivalent to the Type 5 password encryption in Cisco IOS software.


The threat can be reduced by restricting SNMP queries to the VCO/4K, but the fixed software provides much better protection. Customers are strongly encouraged to upgrade to VCO/4K software version 5.1.4 as soon as possible, and to version 5.2 as soon as it becomes available.

Obtaining Fixed Software

Cisco has made free software available to address this vulnerability for affected customers. 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, or as otherwise set forth at Downloads at

Do not contact either "" or "" for software upgrades.

Customers with Service Contracts

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

Customers Using Third-Party Support Organizations

Customers whose Cisco products are provided or maintained through prior or existing agreement 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 Without Service Contracts

Customers who purchase direct from Cisco but who 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 obtain software patches and bug fixes by contacting the Cisco Technical Assistance Center (TAC). 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:

Have your product serial number available and provide the URL of this notice as evidence of entitlement to a software patch or bug fix. Customers without service contracts should request a software patch or bug fix through the TAC.

Refer to for additional TAC contact information, including special localized telephone numbers and instructions and e-mail addresses for use in various languages.

Exploitation and Public Announcements

This vulnerability was reported to the Cisco PSIRT by @Stake, Inc., which discovered it during an audit of a customer network.

The Cisco PSIRT is not aware of any malicious use of this vulnerability.

Status of This Notice: Final


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 will be posted on Cisco's worldwide website at

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.

  • (includes CERT/CC)
  • Various internal Cisco mailing lists

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.

Revision History

Revision 1.0


Initial public release.

Cisco Security Procedures

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 This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at

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