Cisco Security Advisory: Cisco Firewall Services Module Crafted Protocol Independent Multicast Message Denial of Service Vulnerability

Type securityvulns
Reporter Securityvulns
Modified 2012-03-18T00:00:00



Cisco Firewall Services Module Crafted Protocol Independent Multicast Message Denial of Service Vulnerability

Advisory ID: cisco-sa-20120314-fwsm

Revision 1.0

For Public Release 2012 March 14 16:00 UTC (GMT) +---------------------------------------------------------------------


The Cisco Catalyst 6500 Series Firewall Services Module (FWSM) contains a Protocol Independent Multicast (PIM) Denial of Service Vulnerability.

Cisco has released free software updates that address this vulnerability. There are no workarounds available that mitigate this vulnerability. This advisory is available at the following link:

Note: The Cisco Adaptive Security Appliance (ASA) and the Cisco Catalyst 6500 ASA Services Module (ASASM) are also affected by this vulnerability.

A separate Cisco Security Advisory has been published to disclose the vulnerabilities that affect the ASA and ASASM. That advisory is available at:

Affected Products

The Cisco Catalyst 6500 Series Firewall Services Module is affected by this vulnerability. Not all versions of released FWSM Software are affected. Consult the "Software Versions and Fixes" section of this security advisory for more information.

Vulnerable Products

For specific version information, refer to the "Software Versions and Fixes" section of this advisory.

Protocol Independent Multicast Denial of Service Vulnerability +-------------------------------------------------------------

The Cisco FWSM is affected by a vulnerability that may cause affected devices to reload during the processing of a PIM message when multicast routing is enabled. Multicast routing is disabled by default, however when multicast routing is enabled on the Cisco FWSM, PIM is automatically enabled on all interfaces. The following command enables multicast routing:

fwsm(config)# multicast-routing

To verify whether PIM is enabled on an interface use the show pim interface command. The following example shows PIM enabled on the "inside" interface:

fwsm# sh pim interface

Address          Interface          PIM  Nbr   Hello  DR         DR
                                         Count Intvl  Prior        inside             on   0     30     1          this system

Products Confirmed Not Vulnerable +--------------------------------

With the exception of the Cisco ASA and the Cisco Catalyst 6500 ASA Services Module, no other Cisco products are currently known to be affected by this vulnerability.


The following section gives additional details about this vulnerability.

Protocol Independent Multicast Denial of Service Vulnerability +-------------------------------------------------------------

Multicast routing is a bandwidth-conserving technology that reduces traffic by simultaneously delivering a single stream of information to multiple recipients.

Protocol Independent Multicast (PIM) is a multicast routing protocol that is independent of any IP routing protocol. PIM can leverage any unicast routing protocols that are in use, including Exterior Gateway Routing Protocol (EIGRP), Open Shortest Path First (OSPF), Border Gateway Protocol (BGP), or static routes, to populate the unicast routing table. PIM uses this unicast routing information to perform the multicast forwarding function, and is IP protocol-independent. Although PIM is called a multicast routing protocol, it actually uses the unicast routing table to perform the Reverse Path Forwarding (RPF) check function instead of building a completely independent multicast routing table. PIM does not send or receive multicast routing updates between routers as do other routing protocols.

A vulnerability exists in the way PIM is implemented that may cause affected devices to reload during the processing of a PIM message when multicast routing is enabled. The vulnerability is due to improper handling of PIM messages. An attacker could exploit this vulnerability by sending a crafted PIM message to the affected system.

This vulnerability is documented in Cisco bug ID CSCtu97367, and has been assigned Common Vulnerabilities ans Exposures (CVE) ID CVE-2012-0356.

Vulnerability Scoring Details

Cisco has scored the vulnerability in this advisory based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this security advisory is in accordance with CVSS version 2.0.

CVSS is a standards-based scoring method that conveys vulnerability severity and helps organizations determine the urgency and priority of a response.

Cisco has provided a base and temporal score. Customers can also compute environmental scores that help determine the impact of the vulnerability in their own networks.

Cisco has provided additional information regarding CVSS at the following link:

Cisco has also provided a CVSS calculator to compute the environmental impact for individual networks at the following link:

  • CSCtu97367 - Protocol-Independent Multicast Denial of Service Vulnerability

CVSS Base Score - 7.8 Access Vector - Network Access Complexity - Low Authentication - None Confidentiality Impact - None Integrity Impact - None Availability Impact - Complete

CVSS Temporal Score - 6.4 Exploitability - Functional Remediation Level - Official-Fix Report Confidence - Confirmed


Protocol Independent Multicast Denial of Service Vulnerability

Successful exploitation of the vulnerability may allow a remote, unauthenticated attacker to cause the affected system to reload.

Software Versions and Fixes

When considering software upgrades, customers are advised to consult the Cisco Security Advisories and Responses archive at:

Customers should review subsequent advisories to determine exposure and a complete upgrade solution.

In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.

Protocol Independent Multicast Denial of Service Vulnerability +-------------------------------------------------------------

+-------------------------------------------------------------------+ | Vulnerability | Major | First Fixed | | | Release | Release | |------------------------------------+---------+--------------------| | | 2.2 | Not Affected | | |---------+--------------------| | | 2.3 | Not Affected | | |---------+--------------------| | | 3.1 | Vulnerable: | | | | Migrate to 3.2 | |Protocol Independent Multicast |---------+--------------------| | Denial of Service Vulnerability | 3.2 | 3.2(23) Available | | | | late March 2012 | | |---------+--------------------| | | 4.0 | Vulnerable: | | | | Migrate to 4.1 | | |---------+--------------------| | | 4.1 | 4.1(8) | +-------------------------------------------------------------------+


Protocol Independent Multicast Denial of Service Vulnerability

There are no workarounds that mitigate this vulnerability.

Obtaining Fixed Software

Cisco has released free software updates that address the vulnerabilities described in this advisory. Prior to deploying software, customers are advised to consult their maintenance providers or check the software for feature set compatibility and known issues that are specific to their environments.

Customers may only install and expect support for feature sets they have purchased. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license at Or as set forth at:

Do not contact or for software upgrades.

Customers with Service Contracts +-------------------------------

Customers with contracts should obtain upgraded software through their regular update channels. For most customers, upgrades should be obtained through the Software Center on at:

Customers Using Third-Party Support Organizations +------------------------------------------------

Customers with Cisco products that are provided or maintained through prior or existing agreements with third-party support organizations, such as Cisco Partners, authorized resellers, or service providers, should contact that organization for assistance with the appropriate course of action.

The effectiveness of any workaround or fix depends on specific customer situations, such as product mix, network topology, traffic behavior, and organizational mission. Because of the variety of affected products and releases, customers should consult their service providers or support organizations to ensure that any applied workaround or fix is the most appropriate in the intended network before it is deployed.

Customers Without Service Contracts +----------------------------------

Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco Technical Assistance Center (TAC):

  • +1 800 553 2447 (toll free from within North America)
  • +1 408 526 7209 (toll call from anywhere in the world)
  • e-mail:

Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade. Customers without service contracts should request free upgrades through the TAC.

Refer to Cisco Worldwide Contacts at: For additional TAC contact information, including localized telephone numbers, instructions, and e-mail addresses for support in various languages.

Exploitation and Public Announcements

The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

The vulnerability described in this security advisory was found during the resolution of a customer support case.

Status of This Notice: Final


A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.


This advisory is posted on Cisco Security Intelligence Operations at the following link:

Additionally, a text version of this advisory is clear signed with the Cisco PSIRT PGP key and circulated among the following e-mail addresses:


Future updates of this advisory, if any, will reside on but may not be announced on mailing lists. Users can monitor this advisory's URL for any updates.

Revision History

+-------------------------------------------------------------------+ | Revision 1.0 | 2012-March-14 | Initial public release | +-------------------------------------------------------------------+

Cisco Security Procedures

Complete information about reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco is available on at: This web page includes instructions for press inquiries regarding Cisco Security Advisories. All Cisco Security Advisories are available at:

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