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AUSCERT External Security Bulletin Redistribution
ESB-2016.3039
Cisco IOS and IOS XE Software SSH X.509 Authentication Bypass Vulnerability
20 December 2016
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco IOS
Cisco IOS XE
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Unauthorised Access -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2016-6474
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20161207-ios-xe-x509
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Cisco Security Advisory
Cisco IOS and IOS XE Software SSH X.509 Authentication Bypass Vulnerability
Medium
Advisory ID: cisco-sa-20161207-ios-xe-x509
First Published: 2016 December 7 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs:CSCuv89417
CVSS Score: Base 5.8, Temporal 4.8
CVE-2016-6474
CWE-287
Summary
A vulnerability in the implementation of X.509 Version 3 for SSH
authentication functionality in Cisco IOS and IOS XE Software could allow an
unauthenticated, remote attacker to bypass authentication on an affected
system.
The vulnerability is due to improper validation of X.509 signatures during
the SSH authentication phase. An attacker could exploit this vulnerability by
presenting an invalid X.509 signature to an affected system. A successful
exploit could allow the attacker to impersonate an existing valid user over an
SSH connection.
There are no workarounds that address this vulnerability.
This advisory is available at the following link:
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20161207-ios-xe-x509
Affected Products
Vulnerable Products This vulnerability affects Cisco IOS and IOS XE
Software. For information about which software releases are vulnerable,
consult the Cisco bug ID at the top of this advisory. Products Confirmed Not
Vulnerable No other Cisco products are currently known to be affected by this
vulnerability.
Workarounds
There are no workarounds that address this vulnerability. As a mitigation,
administrators may disable the X.509 authentication feature on an affected
device until the device is upgraded to a fixed release of the software.
Fixed Software
For information about fixed software releases, consult the Cisco bug ID at
the top of this advisory.
When considering software upgrades, customers are advised to regularly
consult the advisories for Cisco products, which are available from the Cisco
Security Advisories and Alerts page, to determine exposure and a complete
upgrade solution.
In all cases, customers should ensure that the devices to be upgraded
contain sufficient memory and confirm that current hardware and software
configurations will continue to be supported properly by the new release. If
the information is not clear, customers are advised to contact the Cisco
Technical Assistance Center (TAC) or their contracted maintenance providers.
Exploitation and Public Announcements
The Cisco Product Security Incident Response Team (PSIRT) is not aware of
any public announcements or malicious use of the vulnerability that is
described in this advisory.
URL
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20161207-ios-xe-x509
Revision History
Version Description Section Status Date
1.0 Initial public release. — Final 2016-December-07
Legal Disclaimer
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND
OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR
MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE
RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
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