Cisco Applied Mitigation Bulletin-
Cisco Response
This Applied Mitigation Bulletin is a companion document to the PSIRT Security Advisory Cisco Prime Central Unauthenticated Username and Password Enumeration Vulnerability and provides identification and mitigation techniques that administrators can deploy on Cisco network devices.
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The Cisco Prime Central 1.0. and 1.1 contains a vulnerability when it processes a specially crafted TCP IP version 4 (IPv4) packet. This vulnerability can be exploited remotely without authentication and without end-user interaction. Successful exploitation of this vulnerability could allow information disclosure, which enables an attacker to learn information about the affected device.
The attack vectors for exploitation are through IPv4 packets using the following protocols and ports:
- HTTPS using TCP port 8443
- HTTPS using TCP port 9090
This vulnerability has been assigned Common Vulnerabilities and Exposures (CVE) identifier CVE-2013-3473.
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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-20130918-pc
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Mitigation Technique Overview
Cisco devices provide a countermeasure for this vulnerability. Administrators are advised to consider this protection method 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 this technique.
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 this vulnerability.
Effective means of 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 this vulnerability.
Cisco IOS NetFlow records can provide visibility into network-based exploitation attempts.
Cisco IOS Software, Cisco ASA, Cisco ASASM, and Cisco FWSM firewalls can provide visibility through syslog messages and counter values displayed in the output from show commands.
The Cisco Security Manager can also provide visibility through incidents, queries, and event reporting.
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Organizations are advised to follow their standard risk evaluation and mitigation processes to determine the potential impact of this vulnerability. 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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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
- Cisco IOS NetFlow and Cisco IOS Flexible NetFlow
- Cisco ASA, Cisco ASASM, and Cisco FWSM Firewalls
- Cisco Security Manager
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 HTTPS IPv4 packets on TCP ports 8443 and 9090 that are sent to affected devices. In the following example,192.168.60.0/24 represent the IP address space that is used by the affected devices, and the host at 192.168.100.1 is considered trusted source 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.
!
!-- Include explicit permit statements for trusted sources that
!-- require access on the vulnerable TCP port(s)
!
access-list 150 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 8443
access-list 150 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 9090
!
!-- 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 8443
access-list 150 deny tcp any 192.168.60.0 0.0.0.255 eq 9090
!
!-- 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 tACLs to interfaces in the ingress direction
!
interface GigabitEthernet0/0
ip access-group 150 inNote that filtering with an interface access list will elicit the transmission of ICMP unreachable messages back to the source of the filtered traffic. Generating these messages could have the undesired effect of increasing CPU utilization on the device. In Cisco IOS Software, ICMP unreachable generation is limited to one packet every 500 milliseconds by default. ICMP unreachable message generation can be disabled using the interface configuration command no ip unreachables. ICMP unreachable rate limiting can be changed from the default using the global configuration command
Identification: Transit Access Control Lists
After the administrator applies the tACL to an interface, show ip access-lists command will identify the number of HTTPS on TCP ports 8443 and 9090 over IPv4 packets on that have been filtered. Administrators are advised to investigate filtered packets to determine whether they are attempts to exploit these vulnerabilities. Example output for show ip access-lists 150 follows:
router#show ip access-lists 150
Extended IP access list 150
10 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 8443
20 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 9090
30 deny tcp any 192.168.60.0 0.0.0.255 eq 8443 (85 matches)
40 deny tcp any 192.168.60.0 0.0.0.255 eq 9090 (56 matches)
50 deny ip any any
router#In the preceding example, access list 150 has dropped the following packets received from an untrusted host or network:
- 85 HTTPS packets on TCP port 8443 for ACE line 30
- 56 HTTPS packets on TCP port 9090 for ACE line 40
Identification: Access List Logging
The log and log-input access control list (ACL) option will cause packets that match specific ACEs to be logged. The log-input option enables logging of the ingress interface in addition to the packet source and destination IP addresses and ports.
Caution: Access control list logging can be very CPU intensive and must be used with extreme caution. Factors that drive the CPU impact of ACL logging are log generation, log transmission, and process switching to forward packets that match log-enabled ACEs.
For Cisco IOS Software, the ip access-list logging interval interval-in-ms command can limit the effects of process switching induced by IPv4 ACL logging. The logging rate-limit rate-per-second [except loglevel] command limits the impact of log generation and transmission.
The CPU impact from ACL logging can be addressed in hardware on the Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers with Supervisor Engine 720 or Supervisor Engine 32 using optimized ACL logging.
For additional information about the configuration and use of ACL logging, reference the Understanding Access Control List Logging Cisco Security Intelligence Operations white paper.
Cisco IOS NetFlow and Cisco IOS FlexibleNetFlow
Identification: IPv4 Traffic Flow Identification Using Cisco IOSNetFlow
Administrators can configure Cisco IOS NetFlow on Cisco IOS routers andswitches to aid in the identification of IPv4 traffic flows that may beattempts to exploit this vulnerability. Administrators are advised toinvestigate flows to determine whether they are attempts to exploit thisvulnerability or whether they are legitimate traffic flows.
router#show ip cache flowIP packet size distribution (90784136 total packets):
1-32 64 96 128 160 192 224 256 288 320 352 384 416 448 480
.000 .698 .011 .001 .004 .005 .000 .004 .000 .000 .003 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .001 .256 .000 .010 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 4456704 bytes
1885 active, 63651 inactive, 59960004 added
129803821 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 402056 bytes
0 active, 16384 inactive, 0 added, 0 added to flow 0
alloc failures, 0 force free 1 chunk, 1 chunk added last clearing of statistics never Protocol Total Flows Packets Bytes Packets Active(Sec) Idle(Sec) -------- Flows /Sec /Flow /Pkt /Sec /Flow /Flow TCP-Telnet 11393421 2.8 1 48 3.1 0.0 1.4 TCP-FTP 236 0.0 12 66 0.0 1.8 4.8 TCP-FTPD 21 0.0 13726 1294 0.0 18.4 4.1 TCP-WWW 22282 0.0 21 1020 0.1 4.1 7.3 TCP-X 719 0.0 1 40 0.0 0.0 1.3 TCP-BGP 1 0.0 1 40 0.0 0.0 15.0 TCP-Frag 70399 0.0 1 688 0.0 0.0 22.7 TCP-other 47861004 11.8 1 211 18.9 0.0 1.3 UDP-DNS 582 0.0 4 73 0.0 3.4 15.4 UDP-NTP 287252 0.0 1 76 0.0 0.0 15.5 UDP-other 310347 0.0 2 230 0.1 0.6 15.9 ICMP 11674 0.0 3 61 0.0 19.8 15.5 IPv6INIP 15 0.0 1 1132 0.0 0.0 15.4 GRE 4 0.0 1 48 0.0 0.0 15.3 Total: 59957957 14.8 1 196 22.5 0.0 1.5 SrcIf SrcIPaddress DstIf DstIPaddress Pr SrcP DstP Pkts Gi0/0 192.168.10.201 Gi0/1 192.168.60.102 06 0984 20FB 98 Gi0/1 192.168.150.60 Gi0/0 10.89.16.226 06 0016 12CA 6 Gi0/0 192.168.13.97 Gi0/1 192.168.60.28 06 0B3E 2382 55 Gi0/0 10.88.226.1 Gi0/1 192.168.202.22 11 007B 007B 7 Gi0/0 10.89.16.226 Gi0/1 192.168.150.60 06 12CA 454 61 router#In the preceding example, there are multiple flows for HTTPS on ports 8443 (hex value 20FB) and 9090 (hex value 2382).
This traffic is sourced from and sent to addresses within the 192.168.60.0/24 address block, which is used by affected devices. Administrators are advised to compare these flows to baseline utilization for HTTPS 8443 and 9090 and also investigate the flows to determine whether they are sourced from untrusted hosts or networks.
As shown in the following example, to view only the HTTPS on ports 8443 (hex value 20FB), 9090 (hex value 2382) use the show ip cache flow | include SrcIf|_06_.*(20FB|2382)_ command to display the related Cisco NetFlow records:
TCP Flowsrouter#show ip cache flow | include SrcIf|_06_.*(20FB|2382)_ SrcIf SrcIPaddress DstIf DstIPaddress Pr SrcP DstP Pkts Gi0/0 192.168.11.131 Gi0/1 192.168.60.245 06 0B66 2382 18 Gi0/0 192.168.41.86 Gi0/1 192.168.60.27 06 0B7B 20FB 22 router#
Identification: IPv4 Traffic Flow Identification Using Cisco Flexible NetFlow
Introduced in Cisco IOS Software Releases 12.2(31)SB2 and 12.4(9)T, Cisco IOS Flexible NetFlow improves original Cisco NetFlow by adding the capability to customize the traffic analysis parameters for the administrator's specific requirements. Original Cisco NetFlow uses a fixed seven tuples of IP information to identify a flow, whereas Cisco IOS Flexible NetFlow allows the flow to be user defined. It facilitates the creation of more complex configurations for traffic analysis and data export by using reusable configuration components.
The following example output is from a Cisco IOS device that is running a version of Cisco IOS Software in the 15.1T train. Although the syntax will be almost identical for the 12.4T and 15.0 trains, it may vary slightly depending on the actual Cisco IOS release being used. In the following configuration, Cisco IOS Flexible NetFlow will collect information on interface GigabitEthernet0/0 for incoming IPv4 flows based on source IPv4 address, as defined by the match ipv4 source address key field statement. Cisco IOS Flexible NetFlow will also include nonkey field information about source and destination IPv4 addresses, protocol, ports (if present), ingress and egress interfaces, and packets per flow.
! !-- Configure key and nonkey fields !-- in the user-defined flow record ! flow record FLOW-RECORD-ipv4 match ipv4 source address collect ipv4 protocol collect ipv4 destination address collect transport source-port collect transport destination-port collect interface input collect interface output collect counter packets ! !-- Configure the flow monitor to
!-- reference the user-defined flow
!-- record
!
flow monitor FLOW-MONITOR-ipv4
record FLOW-RECORD-ipv4
!
!-- Apply the flow monitor to the interface
!-- in the ingress direction
!interface GigabitEthernet0/0 ip flow monitor FLOW-MONITOR-ipv4 inputThe Cisco IOS Flexible NetFlow flow output is as follows:
router#show flow monitor FLOW-MONITOR-ipv4 cache format table Cache type: Normal Cache size: 4096 Current entries: 6 High Watermark: 1 Flows added: 9181 Flows aged: 9175 - Active timeout ( 1800 secs) 9000 - Inactive timeout ( 15 secs) 175 - Event aged 0 - Watermark aged 0 - Emergency aged 0 IPV4 SRC ADDR ipv4 dst addr trns src port trns dst port intf input intf output pkts ip prot =============== =============== ============= ============= ========== =========== ====== ======= 192.168.10.201 192.168.60.102 1456 8443 Gi0/0 Gi0/1 1128 8 192.168.11.54 192.168.60.158 123 453 Gi0/0 Gi0/1 2212 6 192.168.150.60 10.89.16.226 2567 443 Gi0/0 Gi0/1 13 6 192.168.13.97 192.168.60.28 3451 9090 Gi0/0 Gi0/1 1 5 192.168.10.17 192.168.60.97 4231 1521 Gi0/0 Gi0/1 146 9 10.88.226.1 192.168.202.22 2678 443 Gi0/0 Gi0/1 10567 6 10.89.16.226 192.168.150.60 3562 80 Gi0/0 Gi0/1 30012 3To only view the HTTPS on TCP ports 8443 and 9090 use the show flow monitor FLOW-MONITOR-ipv4 cache format table | include IPV4
DST ADDR |_(8443|9090)_.*_06_ command to display the related NetFlow records.For more information about Cisco IOS Flexible NetFlow, refer to Flexible Netflow Configuration Guide, Cisco IOS Release 15M&T and Cisco IOS Flexible NetFlow Configuration Guide, Release 12.4T.
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 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 HTTPS 8443 and 9090 over IPv4 that are sent to affected devices. In the following example, 192.168.60.0/24 represent the IP address space that is used by the affected devices, and the hosts at 192.168.100.1 is considered a trusted source 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.
! !-- Include explicit permit statements for trusted sources !-- that require access on the vulnerable TCP port(s) ! access-list tACL-Policy extended permit tcp host 192.168.100.1 192.168.60.0 255.255.255.0 eq 8443 access-list tACL-Policy extended permit tcp host 192.168.100.1 192.168.60.0 255.255.255.0 eq 9090 ! !-- The following vulnerability-specific access control entries !-- (ACEs) can aid in identification of attacks ! access-list tACL-Policy extended deny tcp any 192.168.60.0 255.255.255.0 eq 8443 access-list tACL-Policy extended deny tcp any 192.168.60.0 255.255.255.0 eq 9090 ! !-- 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 any ! ! !-- Apply tACLs to interfaces in the ingress direction ! access-group tACL-Policy in interface outside
Identification: Transit Access Control Lists
After the tACL has been applied to an interface, administrators can use the show access-list command to identify the number of HTTPS on TCP ports 8443 and 9090 over IPv4 packets that have been filtered. Administrators are advised to investigate filtered packets to determine whether they are attempts to exploit these vulnerabilities. Example output for show access-list tACL-Policy follows:
firewall#show access-list tACL-Policy access-list tACL-Policy; 5 elements; name hash: 0x3452703d access-list tACL-Policy line 1 extended permit tcp host 192.168.100.1 192.168.60.0 255.255.255.0 eq 8443 (hitcnt=31) access-list tACL-Policy line 2 extended permit tcp host 192.168.100.1 192.168.60.0 255.255.255.0 eq 9090 (hitcnt=61) access-list tACL-Policy line 3 extended deny tcp any 192.168.60.0 255.255.255.0 eq 8443 (hitcnt=8) access-list tACL-Policy line 4 extended deny tcp any 192.168.60.0 255.255.255.0 eq 9090 (hitcnt=14)
access-list tACL-Policy line 5 extended deny ip any any (hitcnt=14)In the preceding example, access list tACL-Policy has dropped the following packets received from an untrusted host or network:
- 8 HTTPS packets on TCP port 8443 for ACE line 3
- 14 HTTPS packets on TCP port 9090 for ACE line 4
In addition, syslog message 106023 can provide valuable information, which includes the source and destination IP address, the source and destination port numbers, and the IP protocol for the denied packet.
Identification: Firewall Access List Syslog Messages
Firewall syslog message 106023 will be generated for packets deniedby an access control entry (ACE) that does not have the log keyword present. Additional information about this syslog message is in Cisco ASA 5500 Series System Log Message, 8.2 - 106023.
Information about configuring syslog for the Cisco ASA 5500 Series AdaptiveSecurity Appliance is in
In the following example, the show logging | grep regex command extracts syslog messages from the logging buffer on the firewall. These messages provide additional information about denied packets that could indicate potential attempts to exploit the vulnerability that is described in this document. It is possible to use different regular expressions with the grep keyword to search for specific data in the logged messages.
Additional information about regular expression syntax is in Creating a Regular Expression.
firewall#show logging | grep 106023 Sep 18 2013 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.18/2944 dst inside:192.168.60.191/8443 by access-group "tACL-Policy" Sep 18 2013 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.200/2945 dst inside:192.168.60.33/8443 by access-group "tACL-Policy" Sep 18 2013 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.88/2949 dst inside:192.168.60.38/9090 by access-group "tACL-Policy" Sep 18 2013 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.175/2950 dst inside:192.168.60.250/9090 by access-group "tACL-Policy" firewall#In the preceding example, the messages logged for the tACL tACL-Policy show HTTPS packets for TCP 8443 and 9090 sent to the address block assigned to the affected devices.
Additional information about syslog messages for Cisco ASA Series Adaptive Security Appliances is in Cisco ASA 5500 Series System Log Messages, 8.2. Additional information about syslog messages for Cisco Catalyst 6500 Series ASA Services Module is in the Analyzing Syslog Messages section of the Cisco ASASM CLI Configuration Guide. Additional information about syslog messages for the Cisco FWSM is in Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Logging System Log Messages.
For additional information about investigating incidents using syslog events, reference the Identifying Incidents Using Firewall and IOS Router Syslog Events Cisco Security Intelligence Operations white paper.
Cisco Security Manager
Identification: Cisco Security Manager
Cisco Security Manager, Event Viewer
Beginning in software version 4.0, Cisco Security Manager can collectsyslogs from Cisco firewalls and provides the Event Viewer, which can query forevents that are related to the vulnerability that is described in thisdocument.
Using the following filters in the Firewall Denied Eventspredefined view in the Event Viewer provides all captured Cisco firewall accesslist deny syslog messages that could indicate potentialattempts to exploit the vulnerability that is described in this document.
- Use the Destination event filter to filter network objects that contain the IP address space that is used by the affected devices (for example, IPv4 address range 192.168.60.0/24).
- Use the Destination Service event filter to filter objects that contain TCP ports 8443 and 9090.
An Event Type ID filter can be used with the Firewall Denied Events predefined view in the Event Viewer to filter the syslog IDs shown in the following list to provide all captured Cisco firewall deny syslog messages that could indicate potential attempts to exploit the vulnerability that is described in this document:
- ASA-4-106023 (ACL deny)
For more information about Cisco Security Manager Events, refer to the Filtering and Querying Events section of the Cisco Security Manager User Guide.
Identification: Event Management System Partner Events
Cisco works with industry-leading Security Information and Event Management (SIEM) companies through the Cisco Developer Network. This partnership helps Cisco deliver validated and tested SIEM systems that address business concerns such as long-term log archiving and forensics, heterogeneous event correlation, and advanced compliance reporting. Security Information and Event Management partner products can be leveraged to collect events from Cisco devices and then query the collected events for the incidents created by the deny syslog messages from firewalls that could indicate potential attempts to exploit the vulnerability that is described in this document. The queries can be made by Sig ID and Syslog ID as shown in the following list:
- ASA-4-106023 (ACL deny)
For more information about SIEM partners, refer to the Security Management System website.
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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 THIS DOCUMENT AT ANY TIME.
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Show LessVersion Description Section Date 1 Initial Release 2013-September-18 16:04 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 Prime Central for Hosted Collaboration Solution 1.0 (Base, .1) | 1.1 (Base)
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.
A standalone copy or paraphrase of the text of this document that omits the distribution URL is an uncontrolled copy and may lack important information or contain factual errors. The information in this document is intended for end users of Cisco products