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Four different Cisco product lines are susceptible to multiple vulnerabilities discovered in the Secure Shell (SSH) protocol version 1.5. These issues have been addressed, and fixes have been integrated into the Cisco products that support this protocol.
By exploiting the weakness in the SSH protocol, it is possible to insert arbitrary commands into an established SSH session, collect information that may help in brute force key recovery, or brute force a session key.
Affected product lines are:
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All devices running Cisco IOSĀ® software supporting SSH. This includes
routers and switches running Cisco IOS software.
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Catalyst 6000 switches running CatOS.
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Cisco PIX Firewall.
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Cisco 11000 Content Service Switch family.
No other Cisco products are vulnerable. It is possible to mitigate this vulnerability by preventing, or having control over, the interception of SSH traffic.
Cisco IOS is not vulnerable to any of known exploits that are currently used to compromise UNIX hosts. For the warning regarding increased scanning activity for hosts running SSH consult CERT/CC
This advisory will be posted at: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20010627-ssh.
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All devices running Cisco IOSĀ® software supporting SSH. This includes
routers and switches running Cisco IOS software.
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Vulnerable Products
The following table depicts the affected products categories.
Product Category
CRC-32 check
Traffic analysis
Key recovery
IOS
Vulnerable CSCdt96253
Vulnerable CSCdt57231
Vulnerable CSCdu37371
PIX
Vulnerable CSCdt73353
Not vulnerable
Not vulnerable
VPN3000
Not vulnerable
Not vulnerable
Not vulnerable
Catalyst 6000
Vulnerable CSCdt72996
Vulnerable CSCdt55357
Not vulnerable
CSS 11000
Vulnerable CSCdv34668
Vulnerable CSCdv34676
Vulnerable CSCdv34679
Per product category, the following software releases are vulnerable:
IOS
All 12.0 and later releases that include support for SSH.
PIX
5.2(5) and 5.3.(1)
CatOS
6.2(0.110)
VPN3000
Not vulnerable
CSS 11000
All WebNS releases prior, but excluding, versions: R4.01 B42s, R4.10 B22s, R5.0 B11s, R5.01 B6s
Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by these vulnerabilities.
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An implementation of SSH in multiple Cisco products are vulnerable to three different vulnerabilities. These vulnerabilities are:
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CRC-32 integrity check vulnerability -- This
vulnerability has been described in a CORE SDI S.A. paper entitled "An attack
on CRC-32 integrity checks of encrypted channels using CBC and CFB modes",
which can be found at http://www.core-sdi.com/soft/ssh/ssh.pdf.
In order for this attack to succeed, an attacker must possess one or two known ciphertext/plaintext pairs. This should not be difficult since every session starts with a greeting screen which is fixed and which can be determined. This also implies that an attacker must be somewhere along the session path in order to be able to sniff the session and collect corresponding ciphertext.
For further technical details, see http://www.core-sdi.com/soft/ssh/ssh.pdf.
While fixing this vulnerability, we have not made the implementation mistake described by VU#945216 (see http://www.kb.cert.org/vuls/id/945216) which is being actively exploited.
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Traffic analysis -- This issue has been described in
an analysis jointly made by Dug Song and Solar Designer. It can be found
at:
http://www.openwall.com/advisories/OW-003-ssh-traffic-analysis.txt, and
is entitled "Passive Analysis of SSH (Secure Shell) Traffic".
To exploit this vulnerability, an attacker must be able to capture packets. When sending a packet using the SSH protocol, it is padded to the next 8-byte boundary, but the exact length of the data (without the padding) is sent unencrypted.
The timing between packets may yield additional information, such as the relative position of a letter on the keyboard, but that depends on overall jitter in the network and the typing habits of the person.
For additional information, please see http://www.openwall.com/advisories/OW-003-ssh-traffic-analysis.txt.
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Key recovery in SSH protocol 1.5 -- This has been
discovered by CORE SDI S.A. and the paper describing it can be viewed at
http://www.securityfocus.com/archive/1/161150.
The subject line is "SSH protocol 1.5 session key recovery vulnerability".
In order to exploit this vulnerability, an attacker must be able to sniff the SSH session and be able to establish a connection to the SSH server. In order to recover the server key, an attacker must perform an additional 2^20+2^19=1572864 connections. Since the key has a lifespan of about an hour, this means that an attacker must perform around 400 connections per second.
For further details, please see http://www.securityfocus.com/archive/1/161150.
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CRC-32 integrity check vulnerability -- This
vulnerability has been described in a CORE SDI S.A. paper entitled "An attack
on CRC-32 integrity checks of encrypted channels using CBC and CFB modes",
which can be found at http://www.core-sdi.com/soft/ssh/ssh.pdf.
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There are no workarounds for these vulnerabilities.
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The following software releases contain fixes for all vulnerabilities.
For CSS 11000 family, all vulnerabilities are fixed in the following software releases:
WebNS
R4.01 B42s, R4.10 B22s, R5.0 B11s, R5.01 B6s
For Catalyst 6000 switches, all vulnerabilities are fixed in the following CatOS releases.
CatOS
6.1(2.13), 6.2(0.111) and 6.3(0.7)PAN
Each row of the table describes a release train and the platforms or products for which it is intended. If a given release train is vulnerable, then the earliest possible releases that contain the fix and the anticipated date of availability for each are listed in the "Rebuild", "Interim", and "Maintenance" columns. A device running any release in the given train that is earlier than the release in a specific column (less than the earliest fixed release) is known to be vulnerable, and it should be upgraded at least to the indicated release or a later version (greater than the earliest fixed release label).
When selecting a release, keep in mind the following definitions:
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Maintenance
Most heavily tested and highly recommended release of any label in a given row of the table.
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Rebuild
Constructed from the previous maintenance or major release in the same train, it contains the fix for a specific defect. Although it receives less testing, it contains only the minimal changes necessary to effect the repair.
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Interim
Built at regular intervals between maintenance releases and receives less testing. Interims should be selected only if there is no other suitable release that addresses the vulnerability, and interim images should be upgraded to the next available maintenance release as soon as possible. Interim releases are not available through manufacturing, and usually they are not available for customer download from CCO without prior arrangement with the Cisco TAC.
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 TAC for assistance as shown in the following section.
More information on Cisco IOS software release names and abbreviations is available at http://www.cisco.com/warp/public/620/1.html.
For PIX Firewall software, use the following table to determine affected and fixed software releases.
Train
Description of Image or Platform
Availability of Fixed Releases*
5.x-based Releases
Rebuild
Interim**
Maintenance
5.2
Early Deployment (ED) for all platforms
5.2(5)203 Available through TAC
5.2.(6) Available in August
5.3
Early Deployment (ED) for all platforms
5.3(1)202 Available through TAC
5.3.(2) Available in August
6.x-based Releases
Rebuild
Interim**
Maintenance
6.0
Early Deployment (ED) for all platforms
6.0(1) Available
For Cisco IOS software, use the following table to determine affected and fixed software releases.
Train
Description of Image or Platform
Availability of Fixed Releases*
12.0-based Releases
Rebuild
Interim**
Maintenance
12.0S
Core/ISP support: GSR, RSP, c7200
12.0(20)S 2001-November
12.1-based Releases
Rebuild
Interim**
Maintenance
12.1
General deployment release for all platforms
SSH not supported
12.1AA
Dial support
SSH not supported
12.1CX
Core/ISP support: GSR, RSP, c7200
SSH not supported
12.1DA
xDSL support: 6100, 6200
SSH not supported
12.1DB
Cisco IOS Software Release 12.1(1)DB supports Cisco?s 6400 Universal Access Concentrator
12.1DC
Cisco IOS Software Release 12.1(1)DC supports Cisco?s 6400 Universal Access Concentrator
12.1E
Core/ISP support: GSR, RSP, c7200
12.1(8a)E 2001-Jul-09
12.1EC
12.1EC is being offered to allow early support of new features on the uBR7200 platform, as well as future support for new Universal Broadband Router headend platforms.
12.1(6.5)EC3
12.1EX
Catalyst 6000 support
12.1(8a)E 2001-Jul-09
12.1EY
Cat8510c, Cat8510m, Cat8540c, Cat8540m, LS1010
12.1(6)EY
12.1EZ
Early Deployment (ED): special image
12.1(6)EZ2
12.1T
Early Deployment(ED): VPN, Distributed Director, various platforms
Not Scheduled
Upgrade recommended to 12.2(1b)
12.1XA
Early Deployment (ED): limited platforms
Not Scheduled
Upgrade recommended to 12.2(1b)
12.1XB
Early Deployment (ED): limited platforms
12.1XC
Early Deployment (ED): limited platforms
Not Scheduled
Upgrade recommended to 12.2(1b)
12.1XD
Early Deployment (ED): limited platforms
Not Scheduled
Upgrade recommended to 12.2(1b)
12.1XE
Early Deployment (ED): limited platforms
12.1XF
Early Deployment (ED): 811 and 813 (c800 images)
12.1(2)XF4 2001-July-09
12.1XG
Early Deployment (ED): 800, 805, 820, and 1600
12.1(2)XF4 2001-July-09
12.1XH
Early Deployment (ED): limited platforms
Not Scheduled
Upgrade recommended to 12.2(1b)
12.1XI
Early Deployment (ED): limited platforms
Not Scheduled
Upgrade recommended to 12.2(1b)
12.1XJ
Early Deployment (ED): limited platforms
Not Scheduled
Upgrade recommended to 12.1(5)YB4
12.1XK
Early Deployment (ED): limited platforms
SSH not supported
12.1XL
Early Deployment (ED): limited platforms
Not Scheduled
Upgrade recommended to 12.2(1b)
12.1XM
Short-lived early deployment release
12.1(4)XM4 2001-June-27
12.1XP
Early Deployment (ED): 1700 and SOHO
12.1(3)XP4
12.1XQ
Short-lived early deployment release
Not Scheduled
Upgrade recommended to 12.2(1b)
12.1XR
Short-lived early deployment release
12.1(5)XR2
12.1XS
Short-lived early deployment release
12.1(5)XS2 2001-July
12.1XT
Early Deployment (ED): 1700 series
12.1(3)XT3
12.1XU
Early Deployment (ED): limited platforms
12.1(5)XU1
12.1XV
Short-lived early deployment release
12.1(5)XV3 2001-July
12.1XW
Short-lived early deployment release
SSH not supported
12.1XX
Short-lived early deployment release
SSH not supported
12.1XY
Short-lived early deployment release
12.1(5)XY6 2001-July
12.1XZ
Short-lived early deployment release
SSH not supported
12.1YA
Short-lived early deployment release
Not Scheduled
Upgrade recommended to 12.2(2)XB 2001-August
12.1YB
Short-lived early deployment release
12.1(5)YB4
12.1YC
Short-lived early deployment release
12.1(5)YC1
12.1YD
Short-lived early deployment release
12.1(5)YD2 2001-June-25
12.1YF
Short-lived early deployment release
12.1(5)YF2
12.2-based Releases
Rebuild
Interim**
Maintenance
12.2
General deployment release for all platforms
12.2(1b)
12.2(1.1)
12.2(3) 2001-August
12.2T
General deployment release for all platforms
12.2(2.2)T
12.2XA
SPLOB
12.2(2)XA 2001-July-02
12.2XD
Short-lived early deployment release
12.2(1)XD1
12.2XE
Short-lived early deployment release
12.2(1)XE
12.2XH
Short-lived early deployment release
12.2(1)XH 2001-June-25
12.2XQ
Short-lived early deployment release
12.2(1)XQ 2001-June-23
Notes
* All dates are estimates and subject to change.
** Interim releases are subjected to less rigorous testing than regular maintenance releases, and may have serious bugs.
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Maintenance
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All three vulnerabilities are publicly known. Please see the Details section for the original announcements.
The Cisco PSIRT is not aware of malicious use of the vulnerabilities described in this advisory.
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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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Revision 1.6
2001-Nov-12
Updated information regarding vulnerability of UNIX hosts in Summary section and implementation mistake VU#945216 in Details section
Revision 1.5
2001-Oct-05
Updated SSH protocol version information in Summary section
Revision 1.4
2001-Oct-04
Updated maintenance release version and date for Cisco IOS software 12.0S train in Software Versions and Fixes section
Revision 1.3
2001-Sept-20
Updated information regarding CSS in Summary, Affected Products and Software Versions and Fixes sections
Revision 1.2
2001-Aug-08
Updated url in Details section
Revision 1.1
2001-June-28
Updated software availability date; added Traffic Analysis author
Revision 1.0
2001-June-27
Initial public release
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