Cisco Security Advisory
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Multiple vulnerabilities exist in the Cisco Firewall Services Module (FWSM) for the Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers that may cause the Cisco FWSM to reload after processing crafted SunRPC or certain TCP packets. Repeated exploitation could result in a sustained DoS condition.
Cisco has released software updates that address these vulnerabilities. Workarounds are available for the vulnerabilities disclosed in this advisory.
Note: These vulnerabilities are independent of each other. A device may be affected by one vulnerability and not affected by another.
This advisory is posted at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100804-fwsm.
Note: The Cisco ASA 5500 Series Adaptive Security Appliances are affected by the SunRPC inspection vulnerabilities described in this advisory. A separate Cisco Security Advisory has been published to disclose this and other vulnerabilities that affect the Cisco ASA 5500 Series Adaptive Security Appliances. The advisory is available at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100804-asa.
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Vulnerable Products
The Cisco Firewall Services Module (FWSM) for the Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers is affected by multiple vulnerabilities. Affected versions of Cisco FWSM Software vary depending on the specific vulnerability.
SunRPC Inspection Denial of Service Vulnerabilities
Cisco FWSM Software version 3.x and 4.x are affected by these vulnerabilities only if SunRPC inspection is enabled. SunRPC inspection is enabled by default.
To check if SunRPC inspection is enabled, use the show service-policy | include sunrpc command and confirm that the command returns output, as shown in the following example:
fwsm#show service-policy | include sunrpc Inspect: sunrpc , packet 0, drop 0, reset-drop 0Alternatively, a device that has SunRPC inspection enabled has a configuration similar to the following:
class-map inspection_default match default-inspection-traffic ! policy-map global_policy class inspection_default ... inspect sunrpc ... ! service-policy global_policy global
Note: The Cisco ASA 5500 Series Adaptive Security Appliances are affected by the SunRPC inspection vulnerabilities described in this advisory. A separate Cisco Security Advisory has been published to disclose this and other vulnerabilities that affect the Cisco ASA 5500 Series Adaptive Security Appliances. The advisory is available at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20100804-asa.
TCP Denial of Service Vulnerability
Cisco FWSM Software version 3.x and 4.x are affected by this vulnerability when configured in multi-mode (with virtual firewalls) and with any of the following features:
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ASDM Administrative Access
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Telnet
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SSH
To verify if the FWSM is running in multiple mode, use the show mode command, as shown in the following example:
FWSM(config)#show mode Security context mode: multiple The flash mode is the SAME as the running mode.
The following commands are used to enable the HTTPS server and allow only hosts on the inside interface with an address in the 192.168.1.0/24 network to create ASDM, SSH or Telnet connections:
asa(config)# http server enable asa(config)# http 192.168.1.0 255.255.255.0 inside asa(config)# telnet 192.168.1.0 255.255.255.0 inside asa(config)# ssh 192.168.1.0 255.255.255.0 inside
Determining Software Versions
To determine the version of Cisco FWSM Software that is running, issue the show module command from Cisco IOS Software or Cisco Catalyst Operating System Software to identify what modules and sub modules are installed on the system.
The following example shows a system with a Cisco FWSM (WS-SVC-FWM-1) installed in slot 2:
switch>show module Mod Ports Card Type Model Serial No. --- ----- -------------------------------------- ------------------ ----------- 1 16 SFM-capable 16 port 1000mb GBIC WS-X6516-GBIC SAL06334NS9 2 6 Firewall Module WS-SVC-FWM-1 SAD10360485 3 8 Intrusion Detection System WS-SVC-IDSM-2 SAD0932089Z 4 4 SLB Application Processor Complex WS-X6066-SLB-APC SAD093004BD 5 2 Supervisor Engine 720 (Active) WS-SUP720-3B SAL0934888E Mod MAC addresses Hw Fw Sw Status --- ---------------------------------- ------ ------------ ------------ ------- 1 0009.11e3.ade8 to 0009.11e3.adf7 5.1 6.3(1) 8.5(0.46)RFW Ok 2 0018.ba41.5092 to 0018.ba41.5099 4.0 7.2(1) 3.2(2)10 Ok 3 0014.a90c.9956 to 0014.a90c.995d 5.0 7.2(1) 5.1(6)E1 Ok 4 0014.a90c.66e6 to 0014.a90c.66ed 1.7 4.2(3) Ok 5 0013.c42e.7fe0 to 0013.c42e.7fe3 4.4 8.1(3) 12.2(18)SXF1 Ok [...]
After locating the correct slot, issue the show module <slot number> command to identify the software version that is running, as shown in the following example:
switch>show module 2 Mod Ports Card Type Model Serial No. --- ----- -------------------------------------- ------------------ ----------- 2 6 Firewall Module WS-SVC-FWM-1 SAD10360485 Mod MAC addresses Hw Fw Sw Status --- ---------------------------------- ------ ------------ ------------ ------- 2 0018.ba41.5092 to 0018.ba41.5099 4.0 7.2(1) 3.2(2)10 Ok [...]
The preceding example shows that the FWSM is running software version 3.2(2)10 as indicated by the column under "Sw."
Note: Recent versions of Cisco IOS Software will show the software version of each module in the output from the show module command; therefore, executing the show module <slot number> command is not necessary.
If a Virtual Switching System (VSS) is used to allow two physical Cisco Catalyst 6500 Series Switches to operate as a single logical virtual switch, the show module switch all command can display the software version of all FWSMs that belong to switch 1 and switch 2. The output from this command will be similar to the output from the show module <slot number> but will include module information for the modules in each switch in the VSS.
Alternatively, version information can be obtained directly from the FWSM through the show version command, as shown in the following example:
FWSM> show version FWSM Firewall Version 3.2(2)10 [...]
Customers who use the Cisco Adaptive Security Device Manager (ASDM) to manage their devices can find the version of the software displayed in the table in the login window or in the upper left corner of the ASDM window. The version notation is similar to the following example.
FWSM Version: 3.2(2)10
Products Confirmed Not Vulnerable
With the exception of Cisco ASA 5500 Series Adaptive Security Appliances, no other Cisco products are currently known to be affected by these vulnerabilities.
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ASDM Administrative Access
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The Cisco FWSM is a high-speed, integrated firewall module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers. The FWSM offers firewall services with stateful packet filtering and deep packet inspection.
SunRPC Inspection Denial of Service Vulnerabilities
The Cisco FWSM is affected by three vulnerabilities that may cause the device to reload during the processing of different crafted SunRPC messages when SunRPC inspection is enabled.
Note: These vulnerabilities are only triggered by transit traffic; traffic that is destined to the device does not trigger these vulnerabilities.
These vulnerabilities are documented in Cisco bug IDs CSCte61710 ( registered customers only) , CSCte61622 ( registered customers only) , and CSCte61662 ( registered customers only) ; and have been assigned Common Vulnerabilities and Exposures (CVE) IDs CVE-2010-2818, CVE-2010-2819, and CVE-2010-2820, respectively.
TCP Denial of Service Vulnerability
You can partition a single FWSM into multiple virtual devices, known as security contexts. Each context has its own security policy, interfaces, and administrators. Multiple contexts are similar to multiple standalone devices. Many features are supported in multiple context mode, which includes routing tables, firewall features, and management.
Cisco FWSM is affected by a denial of service vulnerability that could allow an unauthenticated attacker to cause a reload when sending a series of TCP packets. The Cisco FWSM is only affected by this vulnerability when is configured in multi-mode (with virtual firewalls) and configured to accept Telnet, SSH or ASDM connections.
Note: A TCP three-way handshake is needed to exploit this vulnerability. This vulnerability is only triggered by traffic that is destined to the affected device; transit traffic does not trigger this vulnerability.
This vulnerability is documented in Cisco bug ID CSCtg68694 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2010-2821.
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The SunRPC inspection vulnerabilities can be mitigated by disabling SunRPC inspection, if it is not required. Administrators can disable SunRPC inspection by issuing the no inspect sunrpc command in class configuration sub-mode within policy-map configuration.
The TCP DoS vulnerability can be mitigated by only allowing trusted hosts to communicate with the FWSM via HTTPs, SSH, or Telnet. For example, the following commands are used to enable the HTTPS server and allow only hosts on the inside interface with an address in the 192.168.1.0/24 network to create ASDM, SSH or Telnet connections:
asa(config)# http server enable asa(config)# http 192.168.1.0 255.255.255.0 inside asa(config)# telnet 192.168.1.0 255.255.255.0 inside asa(config)# ssh 192.168.1.0 255.255.255.0 inside
Additional mitigation techniques that can be deployed on Cisco devices within the network are available in the Cisco Applied Mitigation Bulletin companion document for this advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20100804-fwsm.
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When considering software upgrades, also consult http://www.cisco.com/go/psirt and any subsequent advisories to determine exposure and a complete upgrade solution.
In all cases, customers should exercise caution to be certain the devices to be upgraded contain sufficient memory and that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, contact the Cisco Technical Assistance Center (TAC) or your contracted maintenance provider for assistance.
Vulnerability
Major Release
First Fixed Release
SunRPC Inspection Denial of Service Vulnerabilities (CSCte61710, CSCte61622, and CSCte61662)
3.1
3.1(17.2)
3.2
3.2(16.1)
4.0
4.0(10.1)
4.1
4.1(1.1)
TCP Denial of Service Vulnerability (CSCtg68694)
3.1
Not vulnerable
3.2
3.2(17.2)
4.0
4.0(11.1)
4.1
4.1(1.2)
Recommended Releases
The following table lists all recommended releases. These recommended releases contain the fixes for all vulnerabilities in this advisory. Cisco recommends upgrading to a release that is equal to or later than these recommended releases.
Major Release
Recommended Release
3.1
3.1(18)
3.2
3.2(18)
4.0
4.0(12)
4.1
4.1(2)
Software Download
Fixed Cisco FWSM Software can be downloaded from the Software Center on Cisco.com by visiting http://www.cisco.com/cisco/web/download/index.html and navigating to Security > Cisco Catalyst 6500 Series Firewall Services Module > Firewall Services Module (FWSM) Software.
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The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory.
These vulnerabilities were found during the troubleshooting of customer service requests and internal testing.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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