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This advisory documents two vulnerabilities for the Cisco PIX firewall. These vulnerabilities are documented as CSCeb20276 (SNMPv3) and CSCec20244/CSCea28896 (VPNC)
There are workarounds available to mitigate the effects of CSCeb20276 (SNMPv3). No workaround is available for CSCec20244/CSCea28896 (VPNC). |
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Credit:
The information has been provided by Cisco Systems Product Security Incident Response Team.
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Affected Products:
All Cisco PIX firewall devices running the affected Cisco PIX firewall software, as documented below, are affected by these vulnerabilities.
* CSCeb20276 (SNMPv3) 6.3.1, 6.2.2 and earlier, 6.1.4 and earlier. 5.x.x and earlier.
* CSCec20244/CSCea28896 (VPNC) 6.2.3 and earlier. 6.1.x and 5.x.x are not affected; they do not implement the VPNC feature.
The Firewall Service Module (FWSM) is also vulnerable to the SNMPv3 issue and is documented as http://www.cisco.com/warp/public/707/cisco-sa-20031215-fwsm.shtml. No other Cisco products are currently known to be affected by these vulnerabilities.
To determine your software revision, type show version at the command line prompt.
Details:
* CSCeb20276 (SNMPv3)
The Cisco PIX firewall crashes and reloads while processing a received SNMPv3 message when snmp-server host <if_name> <ip_addr> or snmp-server host <if_name> <ip_addr> poll is configured on the Cisco PIX firewall. This happens even though the Cisco PIX firewall does not support SNMPv3.
A Cisco PIX firewall configured to only generate and send traps using the snmp-server host <if_name> <ip_addr> trap command is not vulnerable.
* CSCec20244/CSCea28896 (VPNC)
Under certain conditions, an established VPNC IPSec tunnel connection is dropped if another IPSec client attempts to initiate an IKE "Phase I" negotiation to the outside interface of the VPN Client configured Cisco PIX firewall.
Only a Cisco PIX firewall configured as a VPN Client is vulnerable to this vulnerability.
A VPNC also referred to as Easy VPN or ezVPN, connection is created when the Cisco PIX firewall is used as a VPN client to connect to a VPN server. An IKE Phase I negotiation is a step in the establishment of an IPSec session.
CSCea28896 resolved this issue for the 6.3.x software releases and CSCec20244 resolved this issue for the 6.2(3.100) and later software releases.
The Internetworking Terms and Cisco Systems Acronyms online guides can be found at http://www.cisco.com/univercd/cc/td/doc/cisintwk/.
These vulnerabilities are documented in the Cisco Bug Toolkit as Bug ID CSCeb20276 (SNMPv3) and CSCec20244/CSCea28896 (VPNC). To access this tool, you must be a registered user and you must be logged in.
Impact:
* CSCeb20276 (SNMPv3)
This vulnerability can be exploited to initiate a Denial of Service attack on the Cisco PIX firewall.
* CSCec20244/CSCea28896 (VPNC)
This vulnerability can be exploited to initiate a Denial of Service attack on sessions established between a Cisco PIX configured as a VPN Client and a VPN server.
Software Versions and Fixes:
* CSCeb20276 (SNMPv3) 6.3.2 and later, 6.2.3 and later, 6.1.5 and later.
* CSCec20244/CSCea28896 (VPNC) 6.3.1 and later, 6.2(3.100) and later.
The procedure to upgrade to the fixed software version is detailed at http://www.cisco.com/univercd/cc/td/doc/product/iaabu/pix/pix_sw/index.htm.
Workarounds:
* CSCeb20276 (SNMPv3)
There are two workarounds available.
o If SNMP polling to the PIX is required on a vulnerable image, one may choose to restrict the polling access to the SNMP server to trusted interfaces and trusted hosts by using this command:
snmp-server host <if_name> <ip_addr> poll
Note: Both Poll and Trap are enabled if one does not specifically use the poll or trap keyword in the command above. The above command cannot prevent a source IP spoofed SNMP request message from exploiting this vulnerability.
o Disable the SNMP server on the Cisco PIX firewall as follows:
clear snmp-server
no snmp-server location
no snmp-server contact
snmp-server community public
no snmp-server enable traps
Note: The Cisco PIX firewall does not allow one to remove the community string altogether. It will always be either public or a user configured string. show snmp will still show snmp-server community public, but this does not mean SNMP is enabled.
More details at http://www.cisco.com/univercd/cc/td/doc/product/iaabu/pix/pix_62/cmdref/s.htm#1026423.
* CSCec20244/CSCea28896 (VPNC)
No workaround. Please upgrade.
The Cisco PSIRT recommends that affected users upgrade to a fixed software version of code.
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