Identifying and Mitigating Exploitation of the Multiple Vulnerabilities in Cisco PGW Softswitch
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Identifying and Mitigating Exploitation of the Multiple Vulnerabilities in Cisco PGW Softswitch
Advisory ID: cisco-amb-20100512-pgw
https://sec.cloudapps.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20100512-pgw
Revision 1.0
For Public Release 2010 May 12 16:00 UTC (GMT)
Contents
Cisco ResponseDevice-Specific Mitigation and Identification
Additional Information
Revision History
Cisco Security Procedures
Related Information
Cisco Response
This Applied Mitigation Bulletin is a companion document to the PSIRT Security Advisory Multiple Vulnerabilities in Cisco PGW Softswitch and provides identification and mitigation techniques that administrators can deploy on Cisco network devices.
Vulnerability Characteristics
There are multiple vulnerabilities in the Cisco PGW 2200 Softswitch series of products. The following subsections summarize these vulnerabilities:
Malformed MGCP packet can crash device: This vulnerability can be exploited remotely without authentication and without end-user interaction. Successful exploitation of this vulnerability may cause the affected device to crash. Repeated attempts to exploit this vulnerability could result in a sustained DoS condition. The attack vector for exploitation is through an Media Gateway Control Protocol (MGCP) packet using UDP port 2427.
This vulnerability has been assigned CVE identifier CVE-2010-0601.
Malformed SIP packet can crash device: This vulnerability can be exploited remotely without authentication and without end-user interaction. Successful exploitation of this vulnerability may cause the affected device to crash. Repeated attempts to exploit this vulnerability could result in a sustained DoS condition.
This vulnerability has been assigned CVE identifier CVE-2010-0602.
Malformed Session Attribute can crash device: This vulnerability can be exploited remotely without authentication and without end-user interaction. Successful exploitation of this vulnerability may cause the affected device to crash. Repeated attempts to exploit this vulnerability could result in a sustained DoS condition.
This vulnerability has been assigned CVE identifier CVE-2010-0603.
Device crash during SIP testing: This vulnerability can be exploited remotely without authentication and without end-user interaction. Successful exploitation of this vulnerability may cause the affected device to crash. Repeated attempts to exploit this vulnerability could result in a sustained DoS condition.
This vulnerability has been assigned CVE identifier CVE-2010-0604.
Device crash while processing overly long message: This vulnerability can be exploited remotely without authentication and without end-user interaction. Successful exploitation of this vulnerability may cause the affected device to crash. Repeated attempts to exploit this vulnerability could result in a sustained DoS condition.
This vulnerability has been assigned CVE identifier CVE-2010-1561.
Device crash while processing malformed Contact Header: This vulnerability can be exploited remotely without authentication and without end-user interaction. Successful exploitation of this vulnerability may cause the affected device to crash. Repeated attempts to exploit this vulnerability could result in a sustained denial of service (DoS) condition.
This vulnerability has been assigned CVE identifier CVE-2010-1562.
Device crash while processing malformed header: This vulnerability can be exploited remotely without authentication and without end-user interaction. Successful exploitation of this vulnerability may cause the affected device to crash. Repeated attempts to exploit this vulnerability could result in a sustained DoS condition.
This vulnerability has been assigned CVE identifier CVE-2010-1563.
Malformed SIP header can crash device: This vulnerability can be exploited remotely without authentication and without end-user interaction. Successful exploitation of this vulnerability may cause the affected device to crash. Repeated attempts to exploit this vulnerability could result in a sustained DoS condition.
This vulnerability has been assigned CVE identifier CVE-2010-1567.
Exhaustion of TCP sockets prevents device from accepting new connections: This vulnerability can be exploited remotely without authentication and without end-user interaction. Successful exploitation of this vulnerability may result in a denial of service condition. Repeated attempts to exploit this vulnerability could result in a sustained DoS condition.
This vulnerability has been assigned CVE identifier CVE-2010-1565.
The attack vectors for exploitation of each of the preceding vulnerabilities are through Session Initiation Protocol (SIP) packets using the following protocols and ports:
- SIP using UDP port 5060
- SIP using TCP port 5060
- SIP using TCP port 5061
Information about vulnerable, unaffected, and fixed software is available in the PSIRT Security Advisory, which is available at the following link: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100512-pgw.
Mitigation Technique Overview
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 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 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.
Cisco IOS NetFlow records can provide visibility into network-based exploitation attempts.
Cisco IOS Software, Cisco ASA, FWSM firewalls, and Cisco ACE Application Control Engine Appliance and Module can provide visibility through syslog messages and counter values displayed in the output from show commands.
Risk Management
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.
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 MGCP packets on UDP port 2427 and SIP packets on UDP port 5060, TCP port 5060, and TCP port 5061 that are sent to affected devices. In the following example, 192.168.60.0/24 is the IP address space that is used by the affected devices, and the host at 192.168.100.1 is considered a trusted source that requires 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 ports ! access-list 150 permit udp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 2427 access-list 150 permit udp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 5060 access-list 150 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 5060 access-list 150 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 5061 ! !-- The following vulnerability-specific access control entries !-- (ACEs) can aid in identification of attacks ! access-list 150 deny udp any 192.168.60.0 0.0.0.255 eq 2427 access-list 150 deny udp any 192.168.60.0 0.0.0.255 eq 5060 access-list 150 deny tcp any 192.168.60.0 0.0.0.255 eq 5060 access-list 150 deny tcp any 192.168.60.0 0.0.0.255 eq 5061 ! !-- 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 interfaces in the ingress direction ! interface GigabitEthernet0/0 ip access-group 150 in
Note 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 ip icmp rate-limit unreachable interval-in-ms.
Identification: Transit Access Control Lists
After the administrator applies the tACL to an interface, the show ip access-lists command will identify the number of MGCP packets on UDP port 2427 and SIP packets on UDP port 5060, TCP port 5060, and TCP port 5061 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 udp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 2427
20 permit udp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 5060
30 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 5060
40 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 5061
50 deny udp any 192.168.60.0 0.0.0.255 eq 2427 (12 matches)
60 deny udp any 192.168.60.0 0.0.0.255 eq 5060 (26 matches)
70 deny tcp any 192.168.60.0 0.0.0.255 eq 5060 (16 matches)
80 deny tcp any 192.168.60.0 0.0.0.255 eq 5061 (40 matches)
50 deny ip any any
router#
In the preceding example, access list 150 has dropped the following packets that are received from an untrusted host or network:
- 12 MGCP packets on UDP port 2427 for ACE line 50
- 26 SIP packets on UDP port 5060 for ACE line 60
- 16 SIP packets on TCP port 5060 for ACE line 70
- 40 SIP packets on TCP port 5061 for ACE line 80
For additional information about investigating incidents using ACE counters and syslog events, reference the Identifying Incidents Using Firewall and IOS Router Syslog Events Applied Intelligence white paper.
Administrators can use Embedded Event Manager to provide instrumentation when specific conditions are met, such as ACE counter hits. The Applied Intelligence white paper Embedded Event Manager in a Security Context provides additional details about how to use this feature.
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 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 Applied Intelligence white paper.
Cisco IOS NetFlow
Identification: Traffic Flow Identification Using NetFlow Records
Administrators can configure Cisco IOS NetFlow on Cisco IOS routers and switches to aid in the identification of traffic flows that may be attempts to exploit these vulnerabilities. Administrators are advised to investigate flows to determine whether they are attempts to exploit these vulnerabilities or whether they are legitimate traffic flows.
router#show ip cache flow
IP 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 11 0984 097B 17
Gi0/0 192.168.11.54 Gi0/1 192.168.60.158 11 0911 13C4 3
Gi0/1 192.168.150.60 Gi0/0 10.89.16.226 06 0016 12CA 1
Gi0/0 192.168.13.97 Gi0/1 192.168.60.28 06 0B3E 13C4 5
Gi0/0 192.168.10.17 Gi0/1 192.168.60.97 06 0B89 13C5 9
Gi0/0 10.88.226.1 Gi0/1 192.168.202.22 11 007B 007B 1
Gi0/0 10.88.228.1 Gi0/1 192.168.201.88 11 007B 00A1 1
Gi0/0 10.89.16.226 Gi0/1 192.168.150.60 06 12CA 0016 1
router#
In the preceding example, there are multiple flows for MGCP on UDP port 2427 (hex value 097B), SIP on UDP port 5060 (hex value 13C4), SIP on TCP port 5060 (hex value 13C4), and SIP on TCP port 5061 (hex value 13C5).
To view only the traffic flows for MGCP packets on UDP port 2427 (hex value 097B), SIP on UDP port 5060 (hex value 13C4), SIP on TCP port 5060 (hex value 13C4), and SIP on TCP port 5061 (hex value 13C5), the commands show ip cache flow | include SrcIf| _11_.*(097B|13C4)_ and show ip cache flow | include SrcIf|_06_.*(13C4|13C5)_ will display the related UDP and TCP NetFlow records respectively, as shown here:
UDP Flows
router#show ip cache flow | include SrcIf|_11_.*(097B|13C4)_ SrcIf SrcIPaddress DstIf DstIPaddress Pr SrcP DstP Pkts Gi0/0 192.168.10.201 Gi0/1 192.168.60.102 11 0984 097B 17 Gi0/0 192.168.11.54 Gi0/1 192.168.60.158 11 0911 13C4 3 router#
TCP Flows
router#show ip cache flow | include SrcIf|_06_.*(13C4|13C5)_ SrcIf SrcIPaddress DstIf DstIPaddress Pr SrcP DstP Pkts Gi0/0 192.168.13.97 Gi0/1 192.168.60.28 06 0B3E 13C4 5 Gi0/0 192.168.10.17 Gi0/1 192.168.60.97 06 0B89 13C5 9 router#
Cisco ASA and 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 MGCP packets on UDP port 2427 and SIP packets on UDP port 5060, TCP port 5060, and TCP port 5061 that are sent to affected devices. In the following example, 192.168.60.0/24 is the IP address space that is used by the affected devices, and the host at 192.168.100.1 is considered a trusted source that requires 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 ports
!
access-list tACL-Policy extended permit udp host 192.168.100.1
192.168.60.0 255.255.255.0 eq 2427
access-list tACL-Policy extended permit udp host 192.168.100.1
192.168.60.0 255.255.255.0 eq 5060
access-list tACL-Policy extended permit tcp host 192.168.100.1
192.168.60.0 255.255.255.0 eq 5060
access-list tACL-Policy extended permit tcp host 192.168.100.1
192.168.60.0 255.255.255.0 eq 5061
!
!-- The following vulnerability-specific access control entries
!-- (ACEs) can aid in identification of attacks
!
access-list tACL-Policy extended deny udp any 192.168.60.0 255.255.255.0 eq 2427
access-list tACL-Policy extended deny udp any 192.168.60.0 255.255.255.0 eq 5060
access-list tACL-Policy extended deny tcp any 192.168.60.0 255.255.255.0 eq 5060
access-list tACL-Policy extended deny tcp any 192.168.60.0 255.255.255.0 eq 5061
!
!-- 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 tACL to interface(s) 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 MGCP packets on UDP port 2427, SIP packets on UDP port 5060, TCP port 5060, and TCP port 5061 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; 9 elements
access-list tACL-Policy line 1 extended permit udp host 192.168.100.1
192.168.60.0 255.255.255.0 eq 2427 (hitcnt=34)
access-list tACL-Policy line 2 extended permit udp host 192.168.100.1
192.168.60.0 255.255.255.0 eq sip (hitcnt=39)
access-list tACL-Policy line 3 extended permit tcp host 192.168.100.1
192.168.60.0 255.255.255.0 eq sip (hitcnt=12)
access-list tACL-Policy line 4 extended permit tcp host 192.168.100.1
192.168.60.0 255.255.255.0 eq 5061 (hitcnt=22)
access-list tACL-Policy line 5 extended deny udp any
192.168.60.0 255.255.255.0 eq 2427 (hitcnt=119)
access-list tACL-Policy line 6 extended deny udp any
192.168.60.0 255.255.255.0 eq sip (hitcnt=19)
access-list tACL-Policy line 7 extended deny tcp any
192.168.60.0 255.255.255.0 eq sip (hitcnt=11)
access-list tACL-Policy line 8 extended deny tcp any
192.168.60.0 255.255.255.0 eq 5061 (hitcnt=29)
access-list tACL-Policy line 3 extended deny ip any any (hitcnt=8)
firewall#
In the preceding example, access list tACL-Policy has dropped the following packets received from an untrusted host or network:
- 119 MGCP packets on UDP port 2427 for ACE line 5
- 19 SIP packets on UDP port 5060 for ACE line6
- 11 SIP packets on TCP port 5060 for ACE line 7
- 29 SIP packets on TCP port 5061for ACE line 8
Identification: Firewall Access List Syslog Messages
Firewall syslog message 106023 will be generated for packets denied by 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 Adaptive Security Appliance is in Monitoring - Configuring Logging. Information about configuring syslog on the FWSM for Cisco Catalyst 6500 Series switches and Cisco 7600 Series routers is in Monitoring the Firewall Services Module.
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 vulnerabilities that are 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
May 12 2010 00:15:13: %ASA-4-106023: Deny udp src outside:192.0.2.18/2944
dst inside:192.168.60.191/2427 by access-group "tACL-Policy"
May 12 2010 00:15:13: %ASA-4-106023: Deny udp src outside:192.0.2.200/2945
dst inside:192.168.60.33/5060 by access-group "tACL-Policy"
May 12 2010 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.99/2946
dst inside:192.168.60.240/5060 by access-group "tACL-Policy"
May 12 2010 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.100/2947
dst inside:192.168.60.115/5061 by access-group "tACL-Policy"
firewall#
In the preceding example, the messages logged for the tACL tACL-Policy show MGCP packets for UDP port 2427 and SIP packets for UDP port 5060, TCP port 5060, and TCP port 5061 sent to the address block assigned to affected devices.
Additional information about syslog messages for ASA security appliances is in Cisco ASA 5500 Series System Log Messages, 8.2. Additional information about syslog messages for the 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 Applied Intelligence white paper.
Additional Information
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.
Revision History
|
Revision 1.0 |
2010-May-12 |
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 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.
Related Information
- Cisco Applied Mitigation Bulletins
- Cisco Security
- Cisco Security IntelliShield Alert Manager Service
- Cisco Guide to Harden Cisco IOS Devices
- Cisco IOS NetFlow - Home Page on Cisco.com
- Cisco IOS NetFlow White Papers
- NetFlow Performance Analysis
- Cisco Network Foundation Protection White Papers
- Cisco Network Foundation Protection Presentations
- Cisco Firewall Products - Home Page on Cisco.com
- Common Vulnerabilities and Exposures (CVE)