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Cisco Security Advisory

Cisco IOS Software Internet Key Exchange Resource Exhaustion Vulnerability

High
Advisory ID:
cisco-sa-20090923-ipsec
First Published:
2009 September 23 16:00 GMT
Version 1.2:
Final
Workarounds:
See below
Cisco Bug IDs:
CSCsy07555
CVE-2009-2868
CWE-399
CVSS Score:
Base 7.8, Temporal 6.4Click Icon to Copy Verbose Score
AV:N/AC:L/Au:N/C:N/I:N/A:C/E:F/RL:OF/RC:C
CVE-2009-2868
CWE-399

Summary

  • Cisco IOS® devices that are configured for Internet Key Exchange (IKE) protocol and certificate based authentication are vulnerable to a resource exhaustion attack. Successful exploitation of this vulnerability may result in the allocation of all available Phase 1 security associations (SA) and prevent the establishment of new IPsec sessions.

    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-ipsec.

    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

Affected Products

  • Cisco IOS devices that are configured for IKE and certificate based authentication are affected, if there are RSA keys present on the device.

    Vulnerable Products

    IKE is enabled by default if IPsec is used. Cisco IOS devices that are configured for IKE will listen on UDP port 500, UDP port 4500 if the device is configured for NAT Traversal (NAT-T), or UDP ports 848 or 4848 if the device is configured for Group Domain of Interpretation (GDOI). The following outputs show a router that is listening on UDP port 500: 

    Router#show ip sockets 
Proto    Remote      Port      Local       Port  In Out Stat TTY OutputIF
....
 17   --listen--          192.168.66.129    500   0   0   11   0 
....

    Or

    Router-#show udp
Proto        Remote      Port      Local       Port  In Out  Stat TTY OutputIF
 17       --listen--          192.0.2.1         500   0   0  1011   0 
 17(v6)   --listen--          --any--           500   0   0 20011   0 
Router#

    IKE configurations that are performing certificate based authentication will display Rivest-Shamir-Adleman Signature as the authentication method in the output of the show crypto isakmp policy command. This output is shown in the following example:

    Router#show crypto isakmp policy                               

Global IKE policy
Default protection suite
        encryption algorithm:   DES - Data Encryption Standard (56 bit keys).
        hash algorithm:         Secure Hash Standard
        authentication method:  Rivest-Shamir-Adleman Signature
        Diffie-Hellman group:   #1 (768 bit)
        lifetime:               86400 seconds, no volume limit

    The show crypto key mypubkey rsa command can be used to check whether there are RSA keys present on the system. This output is shown in the following example:

    Router#show crypto key mypubkey rsa
% Key pair was generated at: 06:07:49 UTC Jan 13 1996
Key name: myrouter.example.com
  Usage: Signature Key
  Key Data:
   005C300D 06092A86 4886F70D 01010105 00034B00 30480241 00C5E23B
   55D6AB22
   04AEF1BA A54028A6 9ACC01C5 129D99E4 64CAB820 847EDAD9 DF0B4E4C
   73A05DD2
   BD62A8A9 FA603DD2 E2A8A6F8 98F76E28 D58AD221 B583D7A4 71020301 0001
 
% Key pair was generated at: 06:07:50 UTC Jan 13 1996 
Key name: myrouter.example.com
  Usage: Encryption Key
  Key Data:
   00302017 4A7D385B 1234EF29 335FC973 2DD50A37 C4F4B0FD 9DADE748
   429618D5
   18242BA3 2EDFBDD3 4296142A DDF7D3D8 08407685 2F2190A0 0B43F1BD 
   9A8A26DB
   07953829 791FCDE9 A98420F0 6A82045B 90288A26 DBC64468 7789F76E EE21

    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 6500 Series device that is running Cisco IOS Software release 12.2(18)SXF7 with an installed image name of s72033_rp-IPSERVICESK9_WAN-M:

    Router#show version 
Cisco Internetwork Operating System Software 
IOS (tm) s72033_rp Software (s72033_rp-IPSERVICESK9_WAN-M), Version 12.2(18)SXF7, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright ©) 1986-2006 by cisco Systems, Inc.
Compiled Thu 23-Nov-06 06:42 by kellythw

    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

    Cisco IOS XR Software is not affected by this vulnerability.

    No other Cisco products are currently known to be affected by this vulnerability.

Details

  • IPsec is an IP security feature that provides robust authentication and encryption of IP packets. IKE is a key management protocol standard that is used in conjunction with the IPsec standard.

    IKE is a hybrid protocol that implements the Oakley and SKEME key exchanges inside the Internet Security Association and Key Management Protocol (ISAKMP) framework. (ISAKMP, Oakley, and SKEME are security protocols that are implemented by IKE.). More information on IKE is available at the following link:

    http://www.cisco.com/en/US/docs/ios/12_1/security/configuration/guide/scdike.html

    A vulnerability exists in the IKE implementation of Cisco IOS Software, if the certificate based authentication method is used. Successful exploitation of this vulnerability may result in the allocation of all available Phase 1 SAs, which may prevent new IPSec sessions from being established.

    Administrators can view Phase 1 SAs that are allocated as a result of exploitation by issuing the show crypto isakmp sa command. The following example displays sample output for this command:

    Router#show crypto isakmp sa
IPv4 Crypto ISAKMP SA
dst             src             state          conn-id slot status
10.48.66.77     10.48.66.6      MM_KEY_EXCH       1004 ACTIVE
10.48.66.77     10.48.66.6      MM_KEY_EXCH       1003 ACTIVE
10.48.66.77     10.48.66.6      MM_KEY_EXCH       1002 ACTIVE
....

    Any allocated SA can be de-allocated up manually by using the clear crypto isakmp <conn-ID> command.

    This vulnerability is addressed by the Cisco Bug IDs CSCsy07555 ( registered customers only) and CSCee72997 ( registered customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2009-2868.

Workarounds

Fixed Software

Exploitation and Public Announcements

  • The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory.

    This vulnerability was reported to Cisco by a customer.

Cisco Security Vulnerability Policy

  • 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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Revision History

  • Revision 1.2

    2009-October-19

    Updated ION software table.

    Revision 1.1

    2009-October-02

    Added crypto key zeroize rsa command as a workaround.

    Revision 1.0

    2009-September-23

    Initial public release

    Show Less

Cisco Security Vulnerability Policy

  • 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.

Subscribe to Cisco Security Notifications

Action Links for This Advisory

Related to This Advisory