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Credit:
The original article can be found at: http://www.cisco.com/warp/public/707/cisco-sa-20100217-asa.shtml
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Vulnerable Systems:
* Cisco ASA 5500 Series Adaptive Security Appliances
To determine whether a vulnerable version of Cisco ASA Software is running on an appliance, administrators can issue the "show version" command-line interface (CLI) command. The following example shows a Cisco ASA 5500 Series Adaptive Security Appliance that is running software version 8.0(4):
ASA#show version
Cisco Adaptive Security Appliance Software Version 8.0(4)
Device Manager Version 6.0(1)
<output truncated>
Customers who use Cisco ASDM to manage devices can locate the software version in the table that is displayed in the login window or upper-left corner of the Cisco ASDM window.
The Cisco Firewall Services Module (FWSM) is affected by some of the vulnerabilities in this advisory. A separate Cisco Security Advisory has been published to disclose the vulnerabilities that affect the FWSM. This advisory is available at
http://www.cisco.com/warp/public/707/cisco-sa-20100217-fwsm.shtml.
Cisco ASA 5500 Series Adaptive Security Appliances are affected by the following vulnerabilities:
* TCP Connection Exhaustion Denial of Service Vulnerability
* Session Initiation Protocol (SIP) Inspection Denial of Service Vulnerabilities
* Skinny Client Control Protocol (SCCP) Inspection Denial of Service Vulnerability
* WebVPN Datagram Transport Layer Security (DTLS) Denial of Service Vulnerability
* Crafted TCP Segment Denial of Service Vulnerability
* Crafted Internet Key Exchange (IKE) Message Denial of Service Vulnerability
* NT LAN Manager version 1 (NTLMv1) Authentication Bypass Vulnerability
These vulnerabilities are not interdependent; a release that is affected by one vulnerability is not necessarily affected by the others.
TCP Connection Exhaustion Denial of Service Vulnerability
+--------------------------------------------------------
Cisco ASA 5500 Series Adaptive Security Appliances may experience a TCP connection exhaustion condition (no new TCP connections are accepted) that can be triggered through the receipt of specific TCP segments during the TCP connection termination phase. Appliances that are running versions 7.1.x, 7.2.x, 8.0.x, 8.1.x, and 8.2.x are affected when they are configured for any of the following features:
* SSL VPNs
* Cisco Adaptive Security Device Manager (ASDM) Administrative Access
* Telnet Access
* SSH Access
* Virtual Telnet
* Virtual HTTP
* Transport Layer Security (TLS) Proxy for Encrypted Voice Inspection
SIP Inspection Denial of Service Vulnerabilities
+-----------------------------------------------
Two denial of service (DoS) vulnerabilities affect the SIP inspection feature of Cisco ASA 5500 Series Adaptive Security Appliances. Versions 7.0.x, 7.1.x, 7.2.x, 8.0.x, 8.1.x, and 8.2.x are affected. SIP inspection is enabled by default.
To check if SIP inspection is enabled, issue the "show service-policy | include sip" command and confirm that some output is returned. Sample output is displayed in the following example:
ciscoasa#show service-policy | include sip
Inspect: sip , packet 0, drop 0, reset-drop 0
Alternatively, an appliance that has SIP 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 sip
...
!
service-policy global_policy global
SCCP Inspection Denial of Service Vulnerability
+----------------------------------------------
A denial of service vulnerability affects the SCCP inspection feature of the Cisco ASA 5500 Series Adaptive Security Appliances. Versions 8.0.x, 8.1.x, and 8.2.x are affected. SCCP inspection is enabled by default.
To check if SCCP inspection is enabled, issue the "show service-policy | include skinny" command and confirm that some output is returned. Sample output is displayed in the following example:
ciscoasa#show service-policy | include skinny
Inspect: skinny , packet 0, drop 0, reset-drop 0
Alternatively, an appliance that has SCCP 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 skinny
...
!
service-policy global_policy global
WebVPN DTLS Denial of Service Vulnerability
+------------------------------------------
Cisco ASA 5500 Series Adaptive Security Appliances are affected by a denial of service vulnerability that exists when WebVPN and DTLS are enabled. Affected versions include 7.1.x, 7.2.x, 8.0.x, 8.1.x, and 8.2.x. Administrators can enable WebVPN with the "enable " command in "webvpn" configuration mode. DTLS can be enabled by issuing the "svc dtls enable" command in "group policy webvpn" configuration mode. The following configuration snippet provides an example of a WebVPN configuration that enables DTLS:
webvpn
enable outside
svc enable
...
!
group-policy internal
group-policy attributes
...
webvpn
svc dtls enable
...
Altough WebVPN is disabled by default, DTLS is enabled by default in recent software releases.
Crafted TCP Segment Denial of Service Vulnerability
+--------------------------------------------------
Cisco ASA 5500 Series Adaptive Security Appliances are affected by a denial of service vulnerability that can be triggered by a malformed TCP segment that transits the appliance. This vulnerability only affects configurations that use the "nailed" option at the end of their static statement. Additionally, traffic that matches "static" statement must also be inspected by a Cisco AIP-SSM (an Intrusion Prevention System (IPS) module) in inline mode. IPS inline operation mode is enabled by using the "ips inline {fail-close | fail-open}" command in "class" configuration mode. Cisco ASA 5500 Series Adaptive Security Appliances that are running software versions 7.0.x, 7.1.x, 7.2.x, 8.0.x, 8.1.x, and 8.2.x are affected.
Crafted IKE Message Denial of Service Vulnerability
+--------------------------------------------------
A crafted IKE message that is sent through an IPsec tunnel that terminates on a Cisco ASA 5500 Series Adaptive Security Appliance could cause all IPsec tunnels that terminate on the same device to be torn down. Versions 7.0.x, 7.1.x, 7.2.x, 8.0.x, 8.1.x, and 8.2.x are affected. IKE is not enabled by default. If IKE is enabled, the "isakmp enable " command appears in the configuration.
NTLMv1 Authentication Bypass Vulnerability
+-----------------------------------------
An authentication bypass vulnerability affects Cisco ASA 5500 Series Adaptive Security Appliances when NTLMv1 authentication is configured. Versions 7.0.x, 7.1.x, 7.2.x, 8.0.x, 8.1.x, and 8.2.x are affected. Administrators can configure NTLMv1 authentication by defining an Authentication, Authorization, and Accounting (AAA) server group that uses the NTLMv1 protocol with the "aaa-server protocol nt" command and then configuring a service that requires authentication to use that AAA server group. To verify that NTLMv1 authentication is enabled and active, issue the "show aaa-server protocol nt" command. Sample output is displayed in the following example:
ciscoasa#show aaa-server protocol nt
Server Group: test
Server Protocol: nt
Server Address: 192.168.10.11
Server port: 139
Server status: ACTIVE, Last transaction (success) at 11:10:08 UTC Fri Jan 29
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