Contents
Cisco Response
Device-Specific Mitigation and Identification
Additional Information
Cisco Security Procedures
Related Information
Alert History
Cisco Response
This Applied Mitigation Bulletin is a companion document to the PSIRT
Security Advisory Cisco Unified Presence and Jabber Extensible
Communications Platform Denial of Service Vulnerability and provides
identification and mitigation techniques that administrators can deploy on
Cisco network devices.
The Cisco Unified Presence and Jabber Extensible Communications Platform (Jabber XCP)
contain a vulnerability when processing a specially crafted Extensible
Messaging and Presence Protocol (XMPP) stream header using IP version 4
(IPv4) or IP version 6 (IPv6). This vulnerability can be exploited
remotely without authentication and without end-user interaction. Successful
exploitation of this vulnerability could result in a denial of service (DoS)
condition. Repeated attempts to exploit this vulnerability could result in a
sustained DoS condition. The attack vector for exploitation is through XMPP
IPv4 and IPv6 packets using TCP port 5222 by default.
This vulnerability has been assigned Common Vulnerabilities and Exposures
(CVE) identifier CVE-2012-3935.
Information about vulnerable, unaffected, and fixed software is available in
the Cisco Security Advisory, which is available at the following link: http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120912-cupxcp.
Cisco devices provide several countermeasures for this vulnerability.
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 this vulnerability.
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 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.
Risk Management
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.
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:
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 this vulnerability when the attack originates from a trusted
source address.
The tACL policy denies unauthorized IPv4 and IPv6 packets on TCP port 5222
that are sent to affected devices. In the following example, 192.168.60.0/24
and 2001:DB8:1:60::/64 represent the IP address space that is used by the
affected devices, and the hosts at 192.168.100.1 and 2001:DB8::100:1 are
considered trusted sources 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
!
access-list 150 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 5222
!
!-- The following vulnerability-specific access control entry
!-- (ACE) can aid in identification of attacks
!
access-list 150 deny tcp any 192.168.60.0 0.0.0.255 eq 5222
!
!-- 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
!
!-- Create the corresponding IPv6 tACL
!
ipv6 access-list IPv6-Transit-ACL-Policy
!
!-- Include explicit permit statements for trusted sources
!-- that require access on the vulnerable TCP port
!
permit tcp host 2001:DB8::100:1 2001:DB8:1:60::/64 eq 5222
!
!-- The following vulnerability-specific ACE can
!-- aid in identification of attacks to global and
!-- link-local addresses
!
deny tcp any 2001:DB8:1:60::/64 eq 5222
!
!-- Permit or deny all other Layer 3 and Layer 4 traffic in
!-- accordance with existing security policies and configurations
!-- and allow IPv6 neighbor discovery packets, which
!-- include neighbor solicitation packets and neighbor
!-- advertisement packets
!
permit icmp any any nd-ns
permit icmp any any nd-na
!
!-- Explicit deny for all other IPv6 traffic
!
deny ipv6 any any
!
!
!-- Apply tACLs to interfaces in the ingress direction
!
interface GigabitEthernet0/0
ip access-group 150 in
ipv6 traffic-filter IPv6-Transit-ACL-Policy 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 commands no ip unreachables and
no ipv6 unreachables. ICMP unreachable rate limiting can be
changed from the default using the global configuration commands ip
icmp rate-limit unreachable interval-in-ms and ipv6
icmp error-interval interval-in-ms.
Identification: Transit Access Control Lists
After the administrator applies the tACL to an interface, show ip
access-lists and show ipv6 access-list commands will
identify the number of XMPP IPv4 and IPv6 packets on TCP port 5222 that have
been filtered. Administrators are advised to investigate filtered packets to
determine whether they are attempts to exploit this vulnerability. Example
output for show ip access-lists 150 and show ipv6
access-list IPv6-Transit-ACL-Policy 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 5222
20 deny tcp any 192.168.60.0 0.0.0.255 eq 5222 (42 matches)
30 deny ip any any
router#
In the preceding example, access list 150 has dropped 42
XMPP packets on TCP port 5222 for
access control list entry (ACE) line 20.
router#show ipv6 access-list IPv6-Transit-ACL-Policy
IPv6 access list IPv6-Transit-ACL-Policy
permit tcp host 2001:DB8::100:1 2001:DB8:1:60::/64 eq 5222 (55 matches) sequence 10
deny tcp any 2001:DB8:1:60::/64 eq 5222 (30 matches) sequence 20
permit icmp any any nd-ns (41 matches) sequence 30
permit icmp any any nd-na (41 matches) sequence 40
deny ipv6 any any (21 matches) sequence 50
In the preceding example, access list IPv6-Transit-ACL-Policy has
dropped 30 XMPP packets on TCP port
5222 for access control list entry (ACE) line 20.
For additional information about investigating incidents using ACE counters
and syslog events, reference the Identifying
Incidents Using Firewall and IOS Router Syslog Events Cisco Security
Intelligence Operations white paper.
Administrators can use Embedded Event Manager to provide instrumentation
when specific conditions are met, such as ACE counter hits. The Cisco Security
Intelligence Operations 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 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.
Identification: IPv4 Traffic Flow Identification Using Cisco IOS
NetFlow
Administrators can configure Cisco IOS NetFlow on Cisco IOS routers and
switches to aid in the identification of IPv4 traffic flows that may be
attempts to exploit this vulnerability. Administrators are advised to
investigate flows to determine whether they are attempts to exploit this
vulnerability 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 06 0984 1466 1
Gi0/0 192.168.11.54 Gi0/1 192.168.60.158 11 0911 00A1 3
Gi0/1 192.168.150.60 Gi0/0 10.89.16.226 11 0016 0035 1
Gi0/0 192.168.13.97 Gi0/1 192.168.60.28 06 0B3E 1466 5
Gi0/0 192.168.10.17 Gi0/1 192.168.60.97 06 0B89 1466 1
Gi0/0 10.88.226.1 Gi0/1 192.168.202.22 06 4652 0050 1
Gi0/0 192.168.12.185 Gi0/1 192.168.60.239 06 0BD7 0050 1
Gi0/0 10.89.16.226 Gi0/1 192.168.150.60 06 12CA 1466 1
router#
In the preceding example, there are multiple flows for XMPP
on TCP port 5222 (hex value 1466).
As shown in the following example, to view only the XMPP packets on TCP port
5222 (hex value 1466), use the show ip cache flow | include
SrcIf|_06_.*1466 command to display the related Cisco NetFlow
records:
TCP Flows
router#show ip cache flow | include SrcIf|_06_.*1466
SrcIf SrcIPaddress DstIf DstIPaddress Pr SrcP DstP Pkts
Gi0/0 192.168.12.110 Gi0/1 192.168.60.163 06 9843 1466 88
Gi0/0 192.168.11.230 Gi0/1 192.168.60.20 06 9844 1466 21
Gi0/0 192.168.11.131 Gi0/1 192.168.60.245 06 9845 1466 18
Gi0/0 192.168.13.7 Gi0/1 192.168.60.162 06 9846 1466 61
router#
Identification: IPv6 Traffic Flow Identification Using Cisco IOS
NetFlow
Administrators can configure Cisco IOS NetFlow on Cisco IOS routers and
switches to aid in the identification of IPv6 traffic flows that may be
attempts to exploit the vulnerability that is described in this document.
Administrators are advised to investigate flows to determine whether they are
attempts to exploit this vulnerability or whether they are legitimate traffic
flows.
The following output is from a Cisco IOS device running Cisco IOS Software
12.4 mainline train. The command syntax will vary for different Cisco IOS
Software trains.
router#show ipv6 flow cache
IP packet size distribution (50078919 total packets):
1-32 64 96 128 160 192 224 256 288 320 352 384 416 448 480
.000 .990 .001 .008 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 475168 bytes
8 active, 4088 inactive, 6160 added
1092984 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 33928 bytes
16 active, 1008 inactive, 12320 added, 6160 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
SrcAddress InpIf DstAddress OutIf Prot SrcPrt DstPrt Packets
2001:DB...06::201 Gi0/0 2001:DB...28::20 Local 0x06 0x6851 0x1466 6461
2001:DB...6A:5BA6 Gi0/0 2001:DB...28::21 Gi0/1 0x3A 0x0000 0x8000 1191
2001:DB...6A:5BA6 Gi0/0 2001:DB...134::3 Gi0/1 0x3A 0x0000 0x8000 1191
2001:DB...6A:5BA6 Gi0/0 2001:DB...128::4 Gi0/1 0x3A 0x0000 0x8000 1192
2001:DB...6A:5BA6 Gi0/0 2001:DB...128::2 Gi0/1 0x06 0x6852 0x1466 2787
2001:DB...06::202 Gi0/0 2001:DB...128::3 Gi0/1 0x06 0x6853 0x1466 3401
2001:DB...06::201 Gi0/0 2001:DB...128::4 Gi0/1 0x11 0x1634 0x13C4 1292
2001:DB...6A:5BA6 Gi0/0 2001:DB...128::3 Gi0/1 0x3A 0x0000 0x8000 1155
2001:DB...6A:5BA6 Gi0/0 2001:DB...146::3 Gi0/1 0x06 0x6854 0x1466 1492
2001:DB...6A:5BA6 Gi0/0 2001:DB...144::4 Gi0/1 0x3A 0x0000 0x8000 1193
To permit display of the full 128-bit IPv6 address, use the terminal
width 132 exec mode command.
In the preceding example, there are multiple IPv6 flows for
XMPP on TCP port 5222 (hex value
1466).
As shown in the following example, to view only the XMPP packets on TCP port
5222 (hex value 1466), use the show ipv6 flow cache | include
SrcIf|_06_.*1466 command to display the related Cisco NetFlow
records:
TCP Flows
router#show ipv6 flow cache | include SrcIf|_06_.*1466
SrcAddress InpIf DstAddress OutIf Prot SrcPrt DstPrt Packets
2001:DB...6A:5BA6 Gi0/0 2001:DB...128::2 Gi0/1 0x06 0x160A 0x1466 1597
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 input
The 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 53 Gi0/0 Gi0/1 1128 17
192.168.11.54 192.168.60.158 123 123 Gi0/0 Gi0/1 2212 17
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 5222 Gi0/0 Gi0/1 91 6
192.168.10.17 192.168.60.97 3452 5222 Gi0/0 Gi0/1 146 6
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 6
To only view the
XMPP packets on TCP port 5222,
use the show flow monitor FLOW-MONITOR-ipv4 cache format table |
include IPV4 DST ADDR |_5222_.*_6_ command to display the related
NetFlow records.
For more information about Cisco IOS Flexible NetFlow, refer to Flexible Netflow Configuration Guide, Cisco IOS Release
15.1M&T and Cisco IOS Flexible NetFlow Configuration Guide, Release
12.4T.
Identification: IPv6 Traffic Flow Identification Using Cisco IOS Flexible
NetFlow
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 IPv6 flows based on the source IPv6 address, as
defined by the match ipv6 source address key field statement.
Cisco IOS Flexible NetFlow will also include nonkey field information about
source and destination IPv6 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-ipv6
match ipv6 source address
collect ipv6 protocol
collect ipv6 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-ipv6
record FLOW-RECORD-ipv6
!
!-- Apply the flow monitor to the interface
!-- in the ingress direction
!
interface GigabitEthernet0/0
ipv6 flow monitor FLOW-MONITOR-ipv6 input
The Cisco IOS Flexible NetFlow flow output is as follows:
router#show flow monitor FLOW-MONITOR-ipv6 cache format table
Cache type: Normal
Cache size: 4096
Current entries: 6
High Watermark: 2
Flows added: 539
Flows aged: 532
- Active timeout ( 1800 secs) 350
- Inactive timeout ( 15 secs) 182
- Event aged 0
- Watermark aged 0
- Emergency aged 0
IPV6 SRC ADDR ipv6 dst addr trns src port trns dst port intf input intf output pkts ip prot
================= ================ ============= ============= ========== =========== ==== =======
2001:DB...06::201 2001:DB...28::20 123 123 Gi0/0 Gi0/0 17 17
2001:DB...06::201 2001:DB...28::20 4856 5222 Gi0/0 Gi0/0 98 6
2001:DB...06::201 2001:DB...28::20 4855 5222 Gi0/0 Gi0/0 87 6
2001:DB...06::201 2001:DB...28::20 2856 5060 Gi0/0 Gi0/0 486 17
2001:DB...06::201 2001:DB...28::20 3012 53 Gi0/0 Gi0/0 1016 17
2001:DB...06::201 2001:DB...28::20 2477 53 Gi0/0 Gi0/0 1563 17
To permit display of the full 128-bit IPv6 address, use the terminal
width 132 exec mode command.
To view only the XMPP packets on TCP port
5222, use the show flow monitor FLOW-MONITOR-ipv6
cache format table | include IPV6 DST ADDR|_5222_.*_6_ command to
display the related Cisco IOS Flexible NetFlow records.
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 this vulnerability
when the attack originates from a trusted source address.
The tACL policy denies unauthorized XMPP IPv4 and IPv6 packets on TCP port
5222 that are sent to affected devices. In the following example,
192.168.60.0/24 and 2001:DB8:1:60::/64 represent the IP address space that is
used by the affected devices, and the hosts at 192.168.100.1 and
2001:DB8::100:1 are considered trusted sources 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
!
access-list tACL-Policy extended permit tcp host 192.168.100.1
192.168.60.0 255.255.255.0 eq 5222
!
!-- The following vulnerability-specific access control entry
!-- (ACE) can aid in identification of attacks
!
access-list tACL-Policy extended deny tcp any 192.168.60.0 255.255.255.0 eq 5222
!
!-- 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
!
!-- Create the corresponding IPv6 tACL
!
!-- Include explicit permit statements for trusted sources
!-- that require access on the vulnerable TCP port
!
ipv6 access-list IPv6-tACL-Policy permit tcp host 2001:DB8::100:1
2001:db8:1:60::/64 eq 5222
!
!-- The following vulnerability-specific access control entry
!-- (ACE) can aid in identification of attacks
!
ipv6 access-list IPv6-tACL-Policy deny tcp any 2001:db8:1:60::/64 eq 5222
!
!-- 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
!
ipv6 access-list IPv6-tACL-Policy deny ip any any
!
!-- Apply tACLs to interfaces in the ingress direction
!
access-group tACL-Policy in interface outside
access-group IPv6-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 XMPP IPv4
and IPv6 packets on TCP port 5222 that have been filtered. Administrators are
advised to investigate filtered packets to determine whether they are attempts
to exploit this vulnerability. Example output for show access-list
tACL-Policy and show access-list IPv6-tACL-Policy
follows:
firewall#show access-list tACL-Policy
access-list tACL-Policy; 3 elements; name hash: 0x383dd03d
access-list tACL-Policy line 1 extended permit tcp host 192.168.100.1
192.168.60.0 255.255.255.0 eq 5222 (hitcnt=31)
access-list tACL-Policy line 2 extended deny tcp any 192.168.60.0
255.255.255.0 eq 5222 (hitcnt=8)
access-list tACL-Policy line 3 extended deny ip any any (hitcnt=8)
In the preceding example, access list tACL-Policy has dropped
8 XMPP packets on TCP port 5222 received from
an untrusted host or network. 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.
firewall#show access-list IPv6-tACL-Policy
ipv6 access-list IPv6-tACL-Policy; 3 elements; name hash: 0x564a2629
ipv6 access-list IPv6-tACL-Policy line 1 permit tcp host 2001:db8:1:100::1
2001:db8:1:60::/64 eq 5222 (hitcnt=30)
ipv6 access-list IPv6-tACL-Policy line 2 deny tcp any
2001:db8:1:60::/64 eq 5222 (hitcnt=29)
ipv6 access-list IPv6-tACL-Policy line 3 deny ip any any (hitcnt=927)
In the preceding example, access list IPv6-tACL-Policy has dropped
29 XMPP packets on TCP port 5222 received
from an untrusted host or network. 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 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 Cisco
Catalyst 6500 Series ASA Services Module is in 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 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 12 2012 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.18/6894
dst inside:192.168.60.191/5222 by access-group "tACL-Policy"
Sep 12 2012 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.200/6895
dst inside:192.168.60.33/5222 by access-group "tACL-Policy"
Sep 12 2012 00:15:13: %ASA-4-106023: Deny tcp src outside:192.0.2.99/6896
dst inside:192.168.60.240/5222 by access-group "tACL-Policy"
firewall#
In the preceding example, the messages logged for the tACL
tACL-Policy show XMPP packets for TCP port
5222 sent to the address block assigned to 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.
Identification: Cisco Security Manager
Cisco Security Manager, Event Viewer
Beginning in software version 4.0, Cisco Security Manager can collect
syslogs from Cisco firewalls and Cisco IPS devices and provides the Event
Viewer, which can query for events that are related to the vulnerability that
is described in this document.
Using the following filters in the Firewall Denied Events
predefined view in the Event Viewer provides all captured Cisco firewall access
list deny syslog messages that could indicate potential
attempts 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 and IPv6 address range
2001:DB8:1:60::/64)
- Use the Destination Service event filter to filter objects that contain
TCP port 5222
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:
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 a Cisco IPS signature or 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:
For more information about SIEM partners, refer to the Security
Management System website.
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.
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 http://www.cisco.com/en/US/products/products_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
