AV:N/AC:L/Au:N/C:N/I:N/A:C/E:F/RL:OF/RC:C
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Cisco IOS® Software contains a vulnerability that could allow an attacker to cause a Cisco IOS device to reload by remotely sending a crafted encryption packet.
Cisco has released software updates that address this vulnerability.
This advisory is posted at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20090923-tls.
Note: The September 23, 2009, Cisco IOS Security Advisory bundled publication includes eleven Security Advisories. Ten of the advisories address vulnerabilities in Cisco IOS Software, and one advisory addresses a vulnerability in Cisco Unified Communications Manager. Each advisory lists the releases that correct the vulnerability or vulnerabilities detailed in the advisory.
Individual publication links are in "Cisco Event Response: Semiannual Cisco IOS Software Advisory Bundled Publication" at the following link:
http://www.cisco.com/web/about/security/intelligence/Cisco_ERP_ sep09.html
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Vulnerable Products
Devices running affected versions of Cisco IOS Software are susceptible if configured with any of the following features:
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Secure Socket Layer (SSL) Virtual Private Network (VPN)
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Secure Shell (SSH)
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Internet Key Exchange (IKE) Encrypted Nonces
Note: Other SSL/HTTPS related features than WebVPN and SSL VPN are not affected by this vulnerability.
To determine whether SSLVPN is enabled on a device, log in to the device and issue the command-line interface (CLI) command show running-config | include webvpn . If the device returns any output then SSLVPN is configured and the device may be vulnerable. Vulnerable configurations vary depending on whether the device is supporting Cisco IOS WebVPN (introduced in Release 12.3(14)T) or Cisco IOS SSLVPNs (introduced in Release 12.4(6)T). The following methods describe how to confirm if the device is vulnerable:
If the output from "show running-config | include webvpn" contains "webvpn enable" then the device is configured with the original Cisco IOS WebVPN. The only way to determine whether the device is vulnerable is to examine the output of "show running-config" to confirm that webvpn is enabled via the command "webvpn enable" and that a "ssl trustpoint" has been configured. The following example shows a vulnerable device configured with Cisco IOS WebVPN:
webvpn enable ! webvpn ssl trustpoint TP-self-signed-29742012
If the output from "show running-config | include webvpn" contains "webvpn gateway <word>" then the device is supporting the Cisco IOS SSLVPN feature. A device is vulnerable if it has the "inservice" command in at least one of the "webvpn gateway" sections. The following example shows a vulnerable device configured with Cisco IOS SSLVPN:
Router# show running | section webvpn webvpn gateway Gateway ip address 10.1.1.1 port 443 ssl trustpoint Gateway-TP inservice ! Router#
A device that supports the Cisco IOS SSLVPN is not vulnerable if it has no "webvpn gateways" configured or all the configured "webvpn gateways" contain the "no inservice" webvpn gateway command.
To determine if SSH is enabled use the show ip ssh command, as shown in the following example:
Router#show ip ssh SSH Enabled - version 1.99 Authentication timeout: 120 secs; Authentication retries: 3 Minimum expected Diffie Hellman key size : 1024 bits
To determine if the IKE encrypted nonces feature is enabled, use the show running-config | include rsa-encr command as follows:
Router#show running-config | inc rsa-encr authentication rsa-encr
To determine the Cisco IOS Software release that is running on a Cisco product, administrators can log in to the device and issue the show version command to display the system banner. The system banner confirms that the device is running Cisco IOS Software by displaying text similar to "Cisco Internetwork Operating System Software" or "Cisco IOS Software." The image name displays in parentheses, followed by "Version" and the Cisco IOS Software release name. Other Cisco devices do not have the show version command or may provide different output.
The following example identifies a Cisco product that is running Cisco IOS Software Release 12.3(26) with an installed image name of C2500-IS-L:
Router#show version Cisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-IS-L), Version 12.3(26), RELEASE SOFTWARE (fc2) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2008 by cisco Systems, Inc. Compiled Mon 17-Mar-08 14:39 by dchih !--- output truncated
The following example identifies a Cisco product that is running Cisco IOS Software Release 12.4(20)T with an installed image name of C1841-ADVENTERPRISEK9-M:
Router#show version Cisco IOS Software, 1841 Software (C1841-ADVENTERPRISEK9-M), Version 12.4(20)T, RELEASE SOFTWARE (fc3) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2008 by Cisco Systems, Inc. Compiled Thu 10-Jul-08 20:25 by prod_rel_team !--- output truncated
Additional information about Cisco IOS Software release naming conventions is available in "White Paper: Cisco IOS Reference Guide" at the following link: http://www.cisco.com/warp/public/620/1.html.
Products Confirmed Not Vulnerable
The Cisco ASA 5500 Series Adaptive Security Appliances are not affected by this vulnerability.
Cisco IOS XR Software is not affected by this vulnerability.
No other Cisco products are currently known to be affected by this vulnerability.
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Secure Socket Layer (SSL) Virtual Private Network (VPN)
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A Cisco IOS device that is configured for SSLVPN or SSH may reload when it receives a specially crafted TCP packet on TCP port 443 (SSLVPN) or TCP port 22 (SSH). Completion of the three-way handshake to the associated TCP port number of these features is required for the vulnerability to be successfully exploited; however, authentication is not required. A Cisco IOS device that is configured for IKE encrypted nonces may reload when it receives a specially crafted UDP packet on port 500 or 4500 (if configured for NAT Traversal (NAT-T)).
This vulnerability is documented in Cisco bug ID CSCsq24002 ( registered customers only) and has been assigned the Common Vulnerabilities and Exposures (CVE) identifier CVE-2009-2871.
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There are no available workarounds other than disabling the affected features and protecting SSH access with the use of VTY access control lists.
Use the no webvpn enable command to disable SSL VPN use.
For Cisco IOS the SSH server can be disabled by applying the command crypto key zeroize rsa while in configuration mode. The SSH server is enabled automatically upon generating an RSA key pair. Zeroing the RSA keys is the only way to completely disable the SSH server.
Access to the SSH server on Cisco IOS Software may also be disabled by removing SSH as a valid transport protocol. This action can be done by reapplying the transport input command with 'ssh' removed from the list of permitted transports on vty lines while in configuration mode. For example:
line vty 0 4 transport input telnet end
If SSH server functionality is desired, access to the server can be restricted to specific source IP addresses or blocked entirely through the use of Access Control Lists (ACLs) on the vty lines as shown in the following URL: http://www.cisco.com/en/US/docs/switches/lan/catalyst2950/software/release/12.1_9_ea1/configuration/guide/swacl.html#xtocid14
More information on configuring ACLs can be found on Cisco's public website:
http://www.cisco.com/en/US/products/sw/secursw/ps1018/products_tech_note09186a00800a5b9a.shtml
The following is an example of a vty access-list:
access-list 2 permit 10.1.1.0 0.0.0.255 access-list 2 deny any line vty 0 4 access-class 2 in
In the previous example, only the 10.1.1.0/24 network is allowed to SSH to the Cisco IOS device.
To disable IKE encrypted nonces use the no authentication rsa-encr command under an ISAKMP policy, as shown in the following example:
crypto isakmp policy no authentication rsa-encr
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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.
Each row of the Cisco IOS software table (below) names a Cisco IOS release train. If a given release train is vulnerable, then the earliest possible releases that contain the fix (along with the anticipated date of availability for each, if applicable) are listed in the "First Fixed Release" column of the table. The "Recommended Release" column indicates the releases which have fixes for all the published vulnerabilities at the time of this Advisory. A device running a release in the given train that is earlier than the release in a specific column (less than the First Fixed Release) is known to be vulnerable. Cisco recommends upgrading to a release equal to or later than the release in the "Recommended Releases" column of the table.
Major Release
Availability of Repaired Releases
Affected 12.0-Based Releases
First Fixed Release
Recommended Release
There are no affected 12.0 based releases.
Affected 12.1-Based Releases
First Fixed Release
Recommended Release
There are no affected 12.1 based releases.
Affected 12.2-Based Releases
First Fixed Release
Recommended Release
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
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Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Please see Cisco IOS-XE Software Availability
Please see Cisco IOS-XE Software Availability
Please see Cisco IOS-XE Software Availability
12.2XND
Please see Cisco IOS-XE Software Availability
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
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Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Affected 12.3-Based Releases
First Fixed Release
Recommended Release
There are no affected 12.3 based releases.
Affected 12.4-Based Releases
First Fixed Release
Recommended Release
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.4(15)MD3
12.4(15)MD3
Not Vulnerable
12.4(19)MR3
12.4(19)MR3
Vulnerable; first fixed in 12.4T
12.4(15)T10
12.4(20)T4
12.4(15)T10
12.4(22)T2
12.4(20)T3
12.4(24)T
12.4(15)T10
12.4(20)T4
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
Vulnerable; first fixed in 12.4T
12.4(15)T10
12.4(20)T4
Not Vulnerable
Vulnerable; first fixed in 12.4T
12.4(15)T10
12.4(20)T4
Vulnerable; first fixed in 12.4T
12.4(15)T10
12.4(20)T4
Not Vulnerable
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.4(15)XQ3
12.4(15)T10
12.4(15)XR5
12.4(15)XR7
12.4(22)XR
Not Vulnerable
Vulnerable; Contact your support organization per the instructions in Obtaining Fixed Software section of this advisory
Vulnerable; first fixed in 12.4T
12.4(15)T10
12.4(20)T4
Vulnerable; first fixed in 12.4T
12.4(15)T10
12.4(20)T4
Vulnerable; first fixed in 12.4T
12.4(15)T10
12.4(20)T4
Vulnerable; first fixed in 12.4T
12.4(15)T10
12.4(20)T4
Not Vulnerable
Not Vulnerable
Not Vulnerable
Note: No Cisco IOS Software Modularity releases are affected by this vulnerability.
Cisco IOS XE Software
IOS XE Release
First Fixed Release
Not Vulnerable
Not Vulnerable
2.3.2
Not Vulnerable
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The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory.
This vulnerability was found during 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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