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Cisco Applied Mitigation Bulletin

Identifying and Mitigating Exploitation of the Cisco Unified Communications Manager and Cisco Unified Contact Center Express Directory Traversal Vulnerabilities

Advisory ID: cisco-amb-20111026-cucm-uccx

http://tools.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20111026-cucm-uccx

Revision 1.0

For Public Release 2011 October 26 16:00  UTC (GMT)


Contents

Cisco Response
Device-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 Advisories Cisco Unified Communications Manager Directory Traversal Vulnerability and Cisco Unified Contact Center Express Directory Traversal Vulnerability and provides identification and mitigation techniques that administrators can deploy on Cisco network devices.

Vulnerability Characteristics

The Cisco Unified Communications Manager and Cisco Unified Contact Center Express contain a vulnerability when processing specially crafted packets. This vulnerability can be exploited remotely without authentication and without end-user interaction. Successful exploitation of this vulnerability may allow information disclosure that could allow an attacker to learn information about the affected device. The attack vector for exploitation is through HTTP packets using TCP port 8080 and TCP port 9080.

This vulnerability has been assigned CVE identifier CVE-2011-3315.

Vulnerability Overview

Information about vulnerable, unaffected, and fixed software is available in the PSIRT Security Advisories, which are available at the following links:

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 this vulnerability.

Effective means of 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

  • tACLs
  • Application layer protocol inspection

These protection mechanisms filter and drop packets that are attempting to exploit this vulnerability.

Effective exploit prevention can also be provided by the Cisco ACE Application Control Engine Appliance and Module using "Application Protocol Inspection".

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, 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.

Effective use of Cisco Intrusion Prevention System (IPS) event actions provides visibility into and protection against attacks that attempt to exploit this vulnerability.

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 this vulnerability when the attack originates from a trusted source address.

The tACL policy denies unauthorized HTTP packets on TCP port 8080 and TCP port 9080 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 tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 8080 access-list 150 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 9080 !
!-- 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 8080 access-list 150 deny tcp any 192.168.60.0 0.0.0.255 eq 9080 !
!-- 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 ipaccess-lists command will identify the number of HTTP packets on TCP port 8080 and TCP port 9080 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 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 8080
    20 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 9080
    30 deny tcp any 192.168.60.0 0.0.0.255 eq 8080 (12 matches)
    40 deny tcp any 192.168.60.0 0.0.0.255 eq 9080 (26 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 HTTP packets on TCP port 8080 for ACE line 30
  • 26 HTTP packets on TCP port 9080 for ACE line 40

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 the vulnerability. Administrators are advised to investigate flows to determine whether they are attempts to exploit the 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 .00

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 1F90 1
Gi0/0 192.168.11.54 Gi0/1 192.168.60.158 06 0911 2378 3
Gi0/1 192.168.150.60 Gi0/0 10.89.16.226 11 0016 12CA 1
Gi0/0 192.168.13.97 Gi0/1 192.168.60.28 06 0B3E 1F90 5
Gi0/0 192.168.10.17 Gi0/1 192.168.60.97 06 0B89 1F90 1
Gi0/0 10.88.226.1 Gi0/1 192.168.202.22 11 007B 007B 1
Gi0/0 192.168.12.185 Gi0/1 192.168.60.239 06 0BD7 2378 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 HTTP on TCP port 8080 (hex value 1F90) and TCP port 9080 (hex value 2378).

To view only the traffic flows for HTTP packets on TCP port 8080 (hex value 1F90) and TCP port 9080 (hex value 2378), the command show ip cache flow | include SrcIf|_06_.*(1F90|2378)_ will display the related TCP NetFlow records  as shown here:

TCP Flows
router#show ip cache flow | include SrcIf|_06_.*(1F90|2378)_
SrcIf         SrcIPaddress     DstIf         DstIPaddress    Pr SrcP DstP  Pkts
Gi0/0 192.168.12.110 Gi0/1 192.168.60.163 06 092A 2378 6
Gi0/0 192.168.11.230 Gi0/1 192.168.60.20 06 0C09 2378 1
Gi0/0 192.168.11.131 Gi0/1 192.168.60.245 06 0B66 1F90 18
Gi0/0 192.168.13.7 Gi0/1 192.168.60.162 06 0914 1F90 1
Gi0/0 192.168.41.86 Gi0/1 192.168.60.27 06 0B7B 2378 2
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 this vulnerability when the attack originates from a trusted source address.

The tACL policy denies unauthorized HTTP packets on TCP port 8080 and TCP port 9080 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 tcp host 192.168.100.1 192.168.60.0 255.255.255.0 eq 8080 access-list tACL-Policy extended permit tcp host 192.168.100.1 192.168.60.0 255.255.255.0 eq 9080 !
!-- 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 8080 access-list tACL-Policy extended deny tcp any 192.168.60.0 255.255.255.0 eq 9080 !
!-- 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

Mitigation: Application Layer Protocol Inspection

Application layer protocol inspection is available beginning in software release 7.2(1) for the Cisco ASA 5500 Series Adaptive Security Appliance and in software release 4.0(1) for the Firewall Services Module. This advanced security feature performs deep packet inspection of traffic that transits the firewall. Administrators may construct an inspection policy for applications that require special handling through the configuration of inspect class maps and inspect policy maps, which are applied via a global or interface service policy.

Additional information about application layer protocol inspection is in the Configuring Application Layer Protocol Inspection section of the Cisco ASA 5500 Series Configuration Guide using the CLI, 8.2.

Caution: Application layer protocol inspection will decrease firewall performance. Administrators are advised to test performance impact in a lab environment before this feature is deployed in production environments.

HTTP Application Inspection
By using the HTTP inspection engine on the Cisco ASA 5500 Series Adaptive Security Appliances and the Firewall Services Module, administrators can configure regular expressions (regexes) for pattern matching and construct inspect class maps and inspect policy maps. These methods can can help protect against specific vulnerabilities, such as the one described in this document, and other threats that may be associated with HTTP traffic. The following HTTP application inspection configuration uses the Cisco Modular Policy Framework (MPF) to create a policy for inspection of traffic on TCP ports 80, 3128, 8000, 8010, 8080, 8888, and 24326, which are the default ports for the Cisco IPS #WEBPORTS variable, in addition to the vulnerable port 9080. The HTTP application inspection policy will drop connections where the HTTP response body contains any of the regexes that are configured to match these vulnerabilities.

Caution: The configured regexes can match text strings at any location in the body of an HTML response. Care should be taken to ensure that legitimate business applications that use matching text strings are not affected. Additional information about regex syntax is in Creating a Regular Expression.

 !
!-- Configure regexes that are associated
!-- with this vulnerability, remember to escape
!-- question marks with ctrl+v
!
regex path-traversal "((\x2e|[%]2(52)?[Ee]|[%]25[%]32([Ee]|[%][46]5)){2}(\x2f|[%]2(52)?[Ff]|[%]25[%]32([Ff]|[%][46]6))){2}" !
!-- Configure an object group for the default ports that
!-- are used by the Cisco IPS #WEBPORTS variable, which
!-- are TCP ports 80 (www), 3128, 8000, 8010, 8080, 8888,
!-- and 24326, in addition to the vulnerable port 9080
!
object-group service WEBPORTS tcp  port-object eq www  port-object eq 3128  port-object eq 8000  port-object eq 8010  port-object eq 8080  port-object eq 8888  port-object eq 9080  port-object eq 24326 !

!-- Configure an access list that uses the WEBPORTS object
!-- group, which will be used to match TCP packets that
!-- are destined to the #WEBPORTS variable that is used
!-- by a Cisco IPS device
!
access-list Webports-ACL extended permit tcp any any object-group WEBPORTS !
!-- Configure a class that uses the above-configured
!-- access list to match TCP packets that are destined
!-- to the ports that are used by the Cisco IPS #WEBPORTS
!-- variable
!
class-map Webports-Class  match access-list Webports-ACL !
!-- Configure an HTTP application inspection policy that
!-- looks for and drops connections that contain HTTP
!-- protocol violations and looks for and drops connections
!-- that contain the regexes for the affected ActiveX Class
!-- ID or Program ID that are configured above
!

policy-map type inspect http http-Policy  parameters !
!-- "protocol-violation" below is not required to
!-- mitigate this vulnerability but is
!-- included to provide more robust protection against
!-- potential HTTP attacks. Care should be taken to ensure that
!-- legitimate applications that do not fully conform to
!-- HTTP protocol standards are not dropped by this inspection
!
  protocol-violation action drop-connection  match request uri regex class path-traversal   drop-connection log !
!-- Add the above-configured "Webports-Class" that matches
!-- TCP packets that are destined to the default ports
!-- that are used by the Cisco IPS #WEBPORTS variable to
!-- the default policy "global_policy" and use it to
!-- inspect HTTP traffic that transits the firewall
!
policy-map global_policy  class Webports-Class   inspect http http-Policy
!
!-- By default, the policy "global_policy" is applied
!-- globally, which results in the inspection of
!-- traffic that enters the firewall from all interfaces
!
service-policy global_policy global

For additional information about the configuration and use of object groups, reference the Cisco ASA 5500 Series Configuration Guide using the CLI, 8.2 for Configuring Object Groups.

Additional information about HTTP application inspection and the MPF is in the HTTP Inspection Overview section of the Cisco ASA 5500 Series Configuration Guide using the CLI, 8.2.

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 HTTP packets on TCP port 8080 and TCP port 9080 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 follows:

firewall#show access-list tACL-Policy
access-list tACL-Policy; 5 elements
access-list tACL-Policy line 1 extended permit tcp host 192.168.100.1 
     192.168.60.0 255.255.255.0 eq 8080 (hitcnt=34)
access-list tACL-Policy line 2 extended permit tcp host 192.168.100.1 
     192.168.60.0 255.255.255.0 eq 9080 (hitcnt=24)
access-list tACL-Policy line 3 extended deny tcp any 
     192.168.60.0 255.255.255.0 eq 8080 (hitcnt=19)
access-list tACL-Policy line 4 extended deny tcp any 
     192.168.60.0 255.255.255.0 eq 9080 (hitcnt=42)
access-list tACL-Policy line 5 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:
  • 19 HTTP packets on TCP port 8080 for ACE line 3
  • 42 HTTP packets on TCP port 9080 for ACE line 4

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 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
  Oct 26 2011 01:03:40: %ASA-4-106023: Deny tcp src outside:192.0.2.18/2944 
         dst inside:192.168.60.191/8080 by access-group "tACL-Policy"
  Oct 26 2011 01:03:40: %ASA-4-106023: Deny tcp src outside:192.0.2.200/2945 
         dst inside:192.168.60.33/9080 by access-group "tACL-Policy"
  Oct 26 2011 01:03:40: %ASA-4-106023: Deny tcp src outside:192.0.2.99/2946 
         dst inside:192.168.60.240/9080 by access-group "tACL-Policy"
  Oct 26 2011 01:03:40: %ASA-4-106023: Deny tcp src outside:192.0.2.100/2947 
         dst inside:192.168.60.115/8080 by access-group "tACL-Policy"
  Oct 26 2011 01:03:40: %ASA-4-106023: Deny tcp src outside:192.0.2.88/2949 
         dst inside:192.168.60.38/9080 by access-group "tACL-Policy"
  Oct 26 2011 01:03:40: %ASA-4-106023: Deny tcp src outside:192.0.2.175/2950 
         dst inside:192.168.60.250/8080 by access-group "tACL-Policy"
firewall#

In the preceding example, the messages logged for the tACL tACL-Policy show HTTP packets for TCP port 8080 and TCP port 9080 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.

Identification: Application Layer Protocol Inspection

Firewall syslog message 415007 will be generated when an HTTP message body matches a user-defined regular expression. The syslog message will identify the corresponding HTTP class and HTTP policy and indicate the action applied to the HTTP connection. Additional information about this syslog message is in Cisco ASA 5500 Series System Log Message, 8.2 - 415007.

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 attempts to exploit this vulnerability. Administrators can 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.

HTTP Application Inspection

firewall#show logging | grep 415007
Oct 26 2011 14:35:54: %ASA-5-415007: HTTP - matched response body regex class vulnerable-regex-class in policy-map http-Policy, Body matched - Dropping connection from outside:192.0.2.117/4369 to inside:192.168.60.65/80
Oct 26 2011 14:36:57: %ASA-5-415007: HTTP - matched response body regex class vulnerable-regex-class in policy-map http-Policy, Body matched - Dropping connection from outside:192.0.2.150/4370 to inside:192.168.60.65/80

With HTTP application inspection enabled, the show service-policy inspect protocol command will identify the number of HTTP packets that are inspected and dropped by this feature. The following example shows output for show service-policy inspect http:

firewall# show service-policy inspect http
Global policy: 
Service-policy: global_policy
Class-map: inspection_default
Class-map: Webports-Class
Inspect: http http-Policy, packet 5025, drop 20, reset-drop 0
protocol violations
packet 0 match response body regex class vulnerable-regex-class
drop-connection log, packet 20
In the preceding example, 5025 HTTP packets have been inspected and 20 HTTP packets have been dropped.

Cisco ACE

Mitigation: Application Protocol Inspection

Application protocol inspection is available for the Cisco ACE Application Control Engine Appliance and Module. This advanced security feature performs deep packet inspection of traffic that transits the Cisco ACE. Administrators can construct an inspection policy for applications that require special handling through the configuration of inspect class maps and inspect policy maps, which are applied via a global or interface service policy.

Additional information about application protocol inspection is in the Configuring Application Protocol Inspection section of the Cisco ACE 4700 Series Appliance Security Configuration Guide.

HTTP Deep Packet Inspection

To conduct HTTP deep packet inspection, administrators can configure regular expressions (regexes) for pattern matching and construct inspect class maps and inspect policy maps. These methods can help protect against specific vulnerabilities, such as the one described in this document, and other threats that may be associated with HTTP traffic. The following HTTP application protocol inspection configuration inspects traffic on TCP ports 80, 3128, 8000, 8010, 8080, 8888, and 24326, which are the default ports for the Cisco IPS #WEBPORTS variable, in addition to the vulnerable port 9080. The HTTP application protocol inspection policy will drop connections where the HTTP content contains any of the regexes that are configured to match the ActiveX control that is associated with this vulnerability.

Caution: The configured regexes can match text strings at any location in the content of an HTML packet. Care should be taken to ensure that legitimate business applications that use matching text strings are not affected.

 ! 
!-- Configure an HTTP application inspection class that
!-- looks for HTTP packets that contain the regexes
!-- that are associated with these vulnerabilities,
!-- remember to escape question marks with ctrl+v
!
!
class-map type http inspect match-any vulnerable-regex-class match url ".*((\x2e|[%]2(52)?[Ee]|[%]25[%]32([Ee]|[%][46]5)){2}(\x2f|[%]2(52)?[Ff]|[%]25[%]32([Ff]|[%][46]6))){2}.*" !
!-- Configure an HTTP application inspection policy that
!-- looks for and resets connections that contain
!-- the regexes for the ActiveX Class ID or
!-- Program ID that are configured above
!
policy-map type inspect http all-match vulnerable-regex-policy class vulnerable-regex-class reset !
!-- Configure an access list that matches TCP packets
!-- that are destined to the #WEBPORTS variable that is
!-- used by a Cisco IPS device, in addition to the
!-- vulnerable port 9080
!
access-list WEBPORTS line 8 extended permit tcp any any eq www access-list WEBPORTS line 16 extended permit tcp any any eq 3128 access-list WEBPORTS line 24 extended permit tcp any any eq 8000 access-list WEBPORTS line 32 extended permit tcp any any eq 8010 access-list WEBPORTS line 40 extended permit tcp any any eq 8080 access-list WEBPORTS line 48 extended permit tcp any any eq 8888 access-list WEBPORTS line 56 extended permit tcp any any eq 9080 access-list WEBPORTS line 64 extended permit tcp any any eq 24326 !
!-- Configure a Layer 4 class that uses the above-configured
!-- access list to match TCP packets that are destined
!-- to the ports that are used by the Cisco IPS #WEBPORTS
!-- variable
!
class-map match-all L4-http-class match access-list WEBPORTS !
!-- Configure a Layer 4 policy that applies the HTTP application
!-- inspection policy configured above to TCP packets that
!-- are destined to the ports that are used by the Cisco IPS
!-- #WEBPORTS variable
!
policy-map multi-match L4-http-inspect-policy class L4-http-class inspect http policy vulnerable-regex-policy !
!-- Apply the configuration to a specific VLAN interface,
!-- which results in the inspection of traffic that enters
!-- the ACE from this interface only
!
!-- The configuration could also be applied globally
!-- which is not shown here
!
interface vlan 200 service-policy input L4-http-inspect-policy

Identification: Application Protocol Inspection

HTTP Deep Packet Inspection

ACE syslog message 415007 will be generated when an HTTP message body matches a user-defined regular expression. The syslog message will identify the corresponding HTTP class and HTTP policy and indicate the action applied to the HTTP connection. Additional information about this syslog message is in Cisco ACE 4700 Series Appliance System Message Guide - System Message 415007

ACE/Admin# show logging | include 415007
Oct 26 2011 15:26:43: %ACE-5-415007: HTTP - matched vulnerable-http-class in policy-map vulnerable-regex-policy, Body matched - Dropping connection from 192.0.2.97/6618 to 192.168.60.65/80 Connection 343
Oct 26 2011 15:30:33: %ACE-5-415007: HTTP - matched vulnerable-http-class in policy-map vulnerable-regex-policy, Body matched - Dropping connection from 192.0.2.97/6618 to 192.168.60.65/8080 Connection 401

When HTTP deep packet inspection is enabled, the show service-policy policyname detail command will identify the number of HTTP connections that are inspected and dropped by this feature. The following example shows output for show service-policy L4-http-inspect-policy detail :

ACE/Admin# show service-policy L4-http-inspect-policy detail


Status     : ACTIVE
-----------------------------------------
Interface: vlan 200 
  service-policy: L4-http-inspect-policy
    class: L4-http-class
            inspect http:
                  L7 inspect policy : vulnerable-regex-policy
                   Url Logging: DISABLED
                   curr conns       : 0         , hit count        : 1         
                   dropped conns    : 0         
                   client pkt count : 3         , client byte count: 589                 
                   server pkt count : 3         , server byte count: 547                 
                   L4 policy stats:
Total Req/Resp: 2 , Total Allowed: 1
Total Dropped : 1 , Total Logged : 0
L7 Inspect policy : vulnerable-regex-policy
class/match : vulnerable-http-class
Inspect action :
reset
Total Inspected : 2 , Total Matched: 1
Total Dropped OnError: 0

In the preceding example, 2 HTTP connections have been inspected and 1 HTTP connection has been dropped.

Additional information about about HTTP Deep Packet Inspection and Application Protocol Inspection is in the Configuring Application Protocol Inspection section of the Cisco ACE 4700 Series Appliance Security Configuration Guide.

Cisco Intrusion Prevention System

Mitigation: Cisco IPS Signature Event Actions

Administrators can use Cisco Intrusion Prevention System (IPS) appliances and services modules to provide threat detection and help prevent attempts to exploit the vulnerability that is described in this document. This vulnerability may be detected by the following signatures:

  • 39986/0 - Cisco Unified Communications Manager Directory Traversal Vulnerability
  • 39946/0 - Cisco Unified Contact Center Express Directory Traversal

39986/0 - Cisco Unified Communications Manager Directory Traversal Vulnerability

Beginning with signature update S605 for sensors running Cisco IPS version 6.x and greater, the vulnerability can be detected by signature 39986/0 (Signature Name: Cisco Unified Communications Manager Directory Traversal Vulnerability). Signature 39986/0 is enabled by default, triggers a Medium severity event, has a signature fidelity rating (SFR) of 85, and is configured with a default event action of produce-alert.

Signature 39986/0 fires when a single packet sent using TCP port 8080 is detected. Firing of this signature may indicate a potential exploit of the vulnerability.


39946-0 - Cisco Unified Contact Center Express Directory Traversal


Beginning with signature update S605 for sensors running Cisco IPS version6.x and greater, the vulnerability can be detected by signature 39946/0(Signature Name: Cisco Unified Contact Center Express Directory Traversal).Signature 39946/0 is enabled by default, triggers a Medium severityevent, has a signature fidelity rating (SFR) of 90, and is configured with a default event action of produce-alert.

Signature 39946/0 fires when a single packet sent using TCP port 8080 or TCP port 9080 is detected. Firing of this signature may indicate a potential exploit of the vulnerability.

Administrators can configure Cisco IPS sensors to perform an event action when an attack is detected. The configured event action performs preventive or deterrent controls to help protect against an attack that is attempting to exploit the vulnerability that is described in this document.

Cisco IPS sensors are most effective when deployed in inline protection mode combined with the use of an event action. Automatic Threat Prevention for Cisco IPS 6.x and greater sensors that are deployed in inline protection mode provides threat prevention against an attack that is attempting to exploit the vulnerability that is described in this document. Threat prevention is achieved through a default override that performs an event action for triggered signatures with a riskRatingValue greater than 90.

For additional information about the risk rating and threat rating calculation, reference Risk Rating and Threat Rating: Simplify IPS Policy Management.

Cisco SecurityMonitoring, Analysis, and Response System

Identification: Cisco Security Monitoring, Analysis, and Response System Incidents

The Cisco Security Monitoring, Analysis, and Response System (Cisco Security MARS) appliance can create incidents regarding events that are related to the vulnerabilities that is described in this document using IPS signature 39986/0 (Signature Name: Cisco Unified Communications Manager Directory Traversal Vulnerability) and IPS signature 39946/0 (Signature Name: Cisco Unified Contact Center Express Directory Traversal). After the S605 dynamic signature update has been downloaded, using keyword NR-39986/0 for IPS signature 39986/0, or keyword NR-39946/0 for IPS signature 39946/0 and a query type of All Matching Events on the Cisco Security MARS appliance will provide a report that lists the incidents created by the IPS signature.

Beginning with the 4.3.1 and 5.3.1 releases of Cisco Security MARS appliances, support for the Cisco IPS dynamic signature updates feature has been added. This feature downloads new signatures from Cisco.com or from a local web server, correctly processes and categorizes received events that match those signatures, and includes them in inspection rules and reports. These updates provide event normalization and event group mapping, and they also enable the MARS appliance to parse new signatures from the IPS devices.

Caution: If dynamic signature updates are not configured, events that match these new signatures appear as unknown event type in queries and reports. Because MARS will not include these events in inspection rules, incidents may not be created for potential threats or attacks that occur within the network.

By default, this feature is enabled but requires configuration. If it is not configured, the following Cisco Security MARS rule will be triggered:

System Rule: CS-MARS IPS Signature Update Failure

When this feature is enabled and configured, administrators can determine the current signature version downloaded by MARS by selecting Help > About and reviewing the IPS Signature Version value.

Additional information about dynamic signature updates and instructions for configuring dynamic signature updates are available for the Cisco Security MARS 4.3.1 and 5.3.1 releases.

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 2011-OCTOBER-26 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 http://www.cisco.com/web/about/security/psirt/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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