Cisco Security Advisory

Unintentional Password Modification Vulnerability in Cisco Firewall Products

Severity
Advisory ID:
cisco-sa-20060823-firewall
First Published:
2006 August 23 16:00 GMT
Version 1.0:
Final

Summary

  • Certain versions of the software for the Cisco PIX 500 Series Security Appliances, the Cisco ASA 5500 Series Adaptive Security Appliances (ASA), and the Firewall Services Module (FWSM) are affected by a software bug that may cause the EXEC password, passwords of locally defined usernames, and the enable password in the startup configuration to be changed without user intervention.

    Unauthorized users can take advantage of this bug to try to gain access to a device that has been reloaded after passwords in its startup configuration have been changed. In addition, authorized users can be locked out and lose the ability to manage the affected device.

    Cisco has made free software available to address this issue for affected customers.

    This advisory is posted at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20060823-firewall.

Affected Products

  • Cisco PIX 500 Series Security Appliances, the Cisco ASA 5500 Series Adaptive Security Appliances, and the Firewall Services Module (FWSM) for the Cisco Catalyst 6500 Switches and Cisco 7600 Series Routers are impacted if they are running an affected software version.

    Vulnerable Products

    The PIX 500 Series Security Appliances and the ASA 5500 Series Adaptive Security Appliances are affected when running any of the following software versions:

    • Any version (including interim versions) in the 7.0(x) train up to and including 7.0(5)
    • Any version (including interim versions) in the 7.1(x) train up to and including 7.1(2.4)

    The FWSM for the Cisco Catalyst 6500 Switches and Cisco 7600 Series Routers is affected when running the following software version:

    • Any version (including interim versions) in the 3.1(x) train up to and including 3.1(1.6)

    Products Confirmed Not Vulnerable

    The PIX 500 Series Security Appliances and the ASA 5500 Series Adaptive Security Appliances are not affected when running any of the following software versions:

    • Any pre-7.x version (PIX only since the ASA does not run pre-7.x code)
    • 7.2(1) and later

    The FWSM for the Cisco Catalyst 6500 Switches and Cisco 7600 Series Routers is not affected when running any of the following software versions:

    • Any 1.x and 2.x version
    • 3.1(2) and later

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

Details

  • The Cisco PIX 500 Series Security Appliances, the Cisco ASA 5500 Series Adaptive Security Appliances, and the Firewall Services Module (FWSM) for the Cisco Catalyst 6500 Switches and Cisco 7600 Series Routers are part of Cisco's security portfolio. All of these products offer firewall services with stateful packet filtering and deep packet inspection. The PIX and ASA devices also offer other services like Virtual Private Networking (VPN), Content Filtering, and Intrusion Prevention.

    On these devices, authentication for both EXEC mode and enable mode can be performed based on Authentication, Authorization, and Accounting (AAA) methods (Remote Authentication Dial-In User Service [RADIUS], Terminal Access Controller Access Control System Plus [TACACS+], or LOCAL). If a device does not have any AAA method (i.e., RADIUS, TACACS+, or LOCAL) configured, authentication for EXEC mode is performed using the password configured with the passwd command, and authentication for enable mode is performed using the password configured with the enable password command.

    A software bug exists in certain versions of the software used by these devices that may cause, under some circumstances, the EXEC password, passwords of locally defined users, and the enable password that are stored in the startup configuration to be changed without user intervention. The startup configuration is stored in a non-volatile medium such as flash memory.

    The affected passwords are set using the following configuration commands:

    • passwd - configures the EXEC password. For example:
      pix(config)# passwd xxxxxxxxx
    • username - configures local users and their associated passwords. For example:
      pix(config)# username admin password xxxxxxxx
    • enable password - configures the password used to enter enable mode. For example:
      pix(config)# enable password xxxxxxxx

    The software bug is known to be triggered in only two scenarios:

    • A software crash, normally caused by a software bug. Please note that not all software crashes may cause the undesired results discussed above.

    • Two or more users making concurrent configuration changes on a device, regardless of the method (command-line interface [CLI], Adaptive Security Device Manager [ASDM], Firewall Management Center, etc.) used to access the device.

      Please note that the passwords in the startup configuration will be changed when the configuration is saved, to the non-volatile medium where the startup configuration is stored, via the write memory or copy running-config startup-config commands. During normal operation, if the running configuration is not saved, passwords in the startup configuration will not change.

    Once the passwords in the startup configuration are changed, administrators will be locked out after the next device reload if authentication for EXEC and for enable privilege depends on the passwords or local accounts stored in the startup configuration. If a AAA server (RADIUS or TACACS+) is used for authentication, the change of passwords in the startup configuration will only cause the undesired results when the AAA server is unavailable, regardless of whether the "LOCAL" authentication method is configured as a fallback, e.g. aaa authentication enable console RADIUS LOCAL.

    Passwords are changed to a non-random value. This behavior is not due to a hardcoded default password or other explicitly induced set of password values, but rather the result of a coding error related to configuration parsing.

    Devices configured in multiple context mode are also affected by this software bug.

    This issue is documented in the following Cisco bug IDs:

Workarounds

Fixed Software

Exploitation and Public Announcements

  • The Cisco PSIRT is not aware of any public announcements or malicious use of the issue described in this advisory, although we are aware that some customers have been impacted by this software bug.

    This issue was brought to Cisco's attention by Terje Bless from Helse Nord IKT. Cisco would like to thank him for working with us towards coordinated disclosure of this issue.

Cisco Security Vulnerability Policy

  • To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.

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URL

Revision History

  • Revision 1.0

    2006-August-23

    Initial public release.

    Show Less

Cisco Security Vulnerability Policy

  • To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.

Subscribe to Cisco Security Notifications

Related to This Advisory