Cisco Secure Access Control System Password Validation Flaw Lets Remote Users Bypass TACACS+ Authentication
SecurityTracker Alert ID: 1027733|
SecurityTracker URL: http://securitytracker.com/id/1027733
(Links to External Site)
Date: Nov 7 2012
Host/resource access via network|
Fix Available: Yes Vendor Confirmed: Yes |
Version(s): 5.0, 5.1, 5.2, 5.3|
A vulnerability was reported in Cisco Secure Access Control System. A remote user can bypass TACACS+ authentication.|
The system does not properly validate user-supplied passwords when TACACS+ is the authentication protocol and the Cisco Secure Access Control System (ACS) is configured with an LDAP external identity store.
A remote user with knowledge of a valid username can send a specially crafted sequence of characters when prompted for the user password to bypass TACACS+ authentication.
Version 5.4 is not affected.
Cisco has assigned Cisco bug ID CSCuc65634 to this vulnerability.
A remote user can bypass TACACS+ authentication.|
The vendor has issued a fix (5.2 Patch 11, 5.3 Patch 7).|
The vendor's advisory is available at:
Vendor URL: tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20121107-acs (Links to External Site)
Source Message Contents
Subject: Cisco Security Advisory: Cisco Secure Access Control System TACACS+ Authentication Bypass Vulnerability|
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Cisco Secure Access Control System TACACS+ Authentication Bypass
Advisory ID: cisco-sa-20121107-acs
For Public Release 2012 November 7 16:00 UTC (GMT)
Cisco Secure Access Control System (ACS) contains a vulnerability that
could allow an unauthenticated, remote attacker to bypass TACACS+
based authentication service offered by the affected product. The
vulnerability is due to improper validation of the user-supplied
password when TACACS+ is the authentication protocol and Cisco Secure
ACS is configured with a Lightweight Directory Access Protocol (LDAP)
external identity store.
An attacker may exploit this vulnerability by sending a special
sequence of characters when prompted for the user password. The
attacker would need to know a valid username stored in the LDAP
external identity store to exploit this vulnerability, and the
exploitation is limited to impersonate only that user. An exploit
could allow the attacker to successfully authenticate to any system
using TACACS+ in combination with an affected Cisco Secure ACS.
Cisco has released free software updates that address this
There are no workarounds for this vulnerability.
This advisory is available at the following link:
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