Cisco Applied Mitigation Bulletin-
This Applied Mitigation Bulletin is a companion document to the PSIRT Security Advisory Multiple Vulnerabilities in Cisco Secure Access Control System and provides identification and mitigation techniques that administrators can deploy on Cisco network devices.
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The Cisco Secure Access Control System (ACS) contains vulnerabilities when processing Remote Method Invocation (RMI) IP version 4 (IPv4) packets. These vulnerabilities can be exploited remotely without authentication and requires end-user interaction. Successful exploitation of these vulnerabilities could allow arbitrary code execution. The Cisco Secure ACS uses RMI for data and configuration replication between ACS servers; therefore, the access control lists (ACL) in this document are applicable between trusted Cisco Secure ACS servers. Client machines do not need access to these TCP ports.
The attack vectors for exploitation are through IPv4 packets using the following protocols and ports:
- RMI using TCP port 2020
- RMI using TCP port 2030
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Information about vulnerable, unaffected, and fixed software is available in the Cisco Security Advisory, which is available at the following link: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20131023-acs.
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Cisco devices provide several countermeasures for these vulnerabilities. Administrators are advised to consider these protection methods to be general security best practices for infrastructure devices and the traffic that transits the network. This section of the document provides an overview of these techniques.
Cisco Secure ACS uses RMI on TCP ports 2020 and 2030 for replication of configuration information and data in a multi-server deployment. Therefore, the trusted addresses in the ACL examples below will include the Cisco Secure ACS addresses. Clients do not need access to RMI ports.
Cisco IOS Software can provide effective means of exploit prevention using Transit Access Control Lists (tACLs). This protection mechanism filters and drops packets that are attempting to exploit these vulnerabilities.
Effective exploit prevention can also be provided by the Cisco ASA 5500 Series Adaptive Security Appliance, Cisco Catalyst 6500 Series ASA Services Module (ASASM), and the Firewall Services Module (FWSM) for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers using Transit Access Control Lists (tACLs). This protection mechanism filters and drops packets that are attempting to exploit these vulnerabilities.
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Organizations are advised to follow their standard risk evaluation and mitigation processes to determine the potential impact of these vulnerabilities. Triage refers to sorting projects and prioritizing efforts that are most likely to be successful. Cisco has provided documents that can help organizations develop a risk-based triage capability for their information security teams. Risk Triage for Security Vulnerability Announcements and Risk Triage and Prototyping can help organizations develop repeatable security evaluation and response processes.
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Device-Specific Mitigation and Identification
Caution:The effectiveness of any mitigation technique depends on specific customer situations such as product mix, network topology, traffic behavior, and organizational mission. As with any configuration change, evaluate the impact of this configuration prior to applying the change.
Specific information about mitigation and identification is available for these devices:
Cisco IOS Routers and Switches
Mitigation: Transit Access Control Lists
To protect the network from traffic that enters the network at ingress access points, which may include Internet connection points, partner and supplier connection points, or VPN connection points, administrators are advised to deploy transit access control lists (tACLs) to perform policy enforcement. Administrators can construct a tACL by explicitly permitting only authorized traffic to enter the network at ingress access points or permitting authorized traffic to transit the network in accordance with existing security policies and configurations. A tACL workaround cannot provide complete protection against these vulnerabilities when the attack originates from a trusted source address.
The tACL policy denies unauthorized IPv4 packets on TCP ports 2020 and 2030 that are sent to affected devices. In the following example, 192.168.60.0/24 represents the IP address space that is used by the affected ACS devices, and the hosts at 192.168.100.1 are also considered trusted Cisco Secure ACS servers that require access to the affected devices. Care should be taken to allow required traffic for routing and administrative access prior to denying all unauthorized traffic.
Additional information about tACLs is in Transit Access Control Lists: Filtering at Your Edge and Identifying the Effectiveness of Security Mitigations Using Cisco IOS Software.
! !-- Include explicit permit statements for trusted sources that !-- require access on the vulnerable TCP ports ! access-list 150 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 2020 access-list 150 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 2030 ! !-- The following vulnerability-specific access control entries !-- (ACEs) can aid in identification of attacks ! access-list 150 deny tcp any 192.168.60.0 0.0.0.255 eq 2020 access-list 150 deny tcp any 192.168.60.0 0.0.0.255 eq 2030 ! !-- Permit or deny all other Layer 3 and Layer 4 traffic in accordance !-- with existing security policies and configurations ! !-- Explicit deny for all other IP traffic ! access-list 150 deny ip any any ! ! ! !-- Apply tACL to interface in the ingress direction ! interface GigabitEthernet0/0 ip access-group 150 in
Additional information about tACLs is in Transit Access Control Lists: Filtering at Your Edge.Cisco ASA, Cisco ASASM, and Cisco FWSM Firewalls
Mitigation: Transit Access Control Lists
To protect the network from traffic that enters the network at ingress access points, which may include Internet connection points, partner and supplier connection points, or VPN connection points, administrators are advised to deploy transit access control lists (tACLs) to perform policy enforcement. Administrators can construct a tACL by explicitly permitting only authorized traffic to enter the network at ingress access points or permitting authorized traffic to transit the network in accordance with existing security policies and configurations. A tACL workaround cannot provide complete protection against these vulnerabilities when the attack originates from a trusted source address.
The tACL policy denies unauthorized IPv4 packets on TCP ports 2020 and 2030 that are sent to affected devices. In the following example, 192.168.60.0/24 represents the IP address space that is used by the affected Cisco Secure ACS devices, and the hosts at 192.168.100.1 are also considered trusted Cisco Secure ACS servers that require access to the affected devices. Care should be taken to allow the required traffic for routing and administrative access prior to denying all unauthorized traffic.
For information about using the Cisco firewall command-line interface to gauge the effectiveness of tACLs, see the Cisco Security white paper Identification of Security Exploits with Cisco ASA, Cisco ASASM, and Cisco FWSM Firewalls.
! !-- Include explicit permit statements for trusted sources !-- that require access on the vulnerable TCP ports ! access-list tACL-Policy extended permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 2020 access-list tACL-Policy extended permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 2030 ! !-- The following vulnerability-specific access control entries !-- (ACEs) can aid in identification of attacks ! access-list tACL-Policy extended deny tcp any 192.168.60.0 0.0.0.255 eq 2020 access-list tACL-Policy extended deny tcp any 192.168.60.0 0.0.0.255 eq 2030 ! !-- Permit or deny all other Layer 3 and Layer 4 traffic in accordance !-- with existing security policies and configurations ! !-- Explicit deny for all other IP traffic ! access-list tACL-Policy extended deny ip any 192.168.60.0 0.0.0.255 !
! ! !-- Apply tACL to interfaces in the ingress direction ! access-group tACL-Policy in interface outside
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Show LessVersion Description Section Date 1 Initial Release 2014-January-15 16:16 GMT
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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 https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html. This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at http://www.cisco.com/go/psirt.
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The security vulnerability applies to the following combinations of products.
Primary Products Cisco Cisco Secure Access Control System (ACS) 5.1 (Base, .0.44) | 5.2 (Base, .0.26, .0.26.1, .0.26.2, .0.26.3, .0.26.4, .0.26.5, .0.26.6, .0.26.7, .0.26.8, .0.26.9, .0.26.10, .0.26.11) | 5.3 (Base, .0.6, .0.40, .0.40.1, .0.40.2, .0.40.3, .0.40.4, .0.40.5, .0.40.6, .0.40.7) | 5.4 (.0.46.0a, .0.46.1, .0.46.2, .0.46.3)
Associated Products
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THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE ALERTS AT ANY TIME.
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