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AUSCERT External Security Bulletin Redistribution
ESB-2015.1609
Cisco IOS XR SSH Disconnect Error Denial of Service Vulnerability
22 June 2015
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco IOS XR
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Existing Account
Resolution: Patch/Upgrade
CVE Names: CVE-2015-4195
Original Bulletin:
http://tools.cisco.com/security/center/viewAlert.x?alertId=39402
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Vulnerability Alert
Cisco IOS XR SSH Disconnect Error Denial of Service Vulnerability
Threat Type: CWE-399: Resource Management Errors
IntelliShield ID: 39402
Version: 1
First Published: 2015 June 18 13:50 GMT
Last Published: 2015 June 18 13:50 GMT
Port: Not available
CVE: CVE-2015-4195
Urgency: Unlikely Use
Credibility: Confirmed
Severity: Mild Damage
CVSS Base: 4.0
CVSS Version 2.0
CVSS Temporal: 3.3
Version Summary: Cisco IOS XR Software contains a vulnerability that could
allow an authenticated, remote attacker to cause a denial of service
condition. Updates are available.
Description
A vulnerability in Cisco IOS XR Software could allow an authenticated, remote
attacker to cause a denial of service (DoS) condition.
The vulnerability is due to an error that could occur in the affected software
when an SSH connection is disconnected from an affected device. An
authenticated, remote attacker could exploit the vulnerability to cause the
vty to become unreachable and cause further SSH or Telnet connections to the
device to fail, resulting in a DoS condition.
Cisco has confirmed the vulnerability and released software updates.
Warning Indicators
At the time this alert was first published, Cisco IOS XR Software Release
5.1.1.K9SEC was vulnerable. Later releases of Cisco IOS XR Software may also
be vulnerable.
IntelliShield Analysis
To exploit this vulnerability, an attacker must authenticate to the targeted
device. This access requirement reduces the likelihood of a successful
exploit.
Cisco indicates through the CVSS score that functional exploit code exists;
however, the code is not known to be publicly available.
Vendor Announcements
Cisco has released bug ID CSCul63127 for registered users, which contains
additional details and an up-to-date list of affected product versions.
Impact
An authenticated, remote attacker could exploit this vulnerability to cause
all SSH or Telnet connections on an affected device to fail, resulting in a
DoS condition.
Technical Information
The vulnerability is due to an error that could occur in the affected software
when an SSH connection is disconnected from an affected device.
An authenticated, remote attacker could exploit this vulnerability to cause
the vty to become unreachable and cause further SSH or Telnet connections to
the device to fail, resulting in a DoS condition.
Safeguards
Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to have network access.
Administrators are advised to allow only privileged users to access
administration or management systems.
Administrators are advised to monitor affected systems.
Patches/Software
Cisco customers with active contracts can obtain updates through the Software
Center at the following link: Cisco. Cisco customers without contracts can
obtain upgrades by contacting the Cisco Technical Assistance Center at
1-800-553-2447 or 1-408-526-7209 or via email at tac@cisco.com.
Alert History
Initial Release
Product Sets
The security vulnerability applies to the following combinations of products.
Primary Products:
Cisco Cisco IOS XR Software 5.1 .1.K9SEC
Associated Products:
N/A
Alerts and bulletins on the Cisco Security Intelligence Operations Portal are
highlighted by analysts in the Cisco Threat Operations Center and represent a
subset of the comprehensive content that is available through Cisco Security
IntelliShield Alert Manager Service. This customizable threat and
vulnerability alert service provides security staff with access to timely,
accurate, and credible information about threats and vulnerabilities that may
affect their environment.
LEGAL DISCLAIMER
The urgency and severity ratings of this alert are not tailored to individual
users; users may value alerts differently based upon their network
configurations and circumstances. THE ALERT, AND INFORMATION CONTAINED
THEREIN, ARE PROVIDED ON AN "AS IS" BASIS AND DO NOT IMPLY ANY KIND OF
GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR USE. YOUR USE OF THE ALERT, AND INFORMATION CONTAINED
THEREIN, OR MATERIALS LINKED FROM THE ALERT, IS AT YOUR OWN RISK. INFORMATION
IN THIS ALERT AND ANY RELATED COMMUNICATIONS IS BASED ON OUR KNOWLEDGE AT THE
TIME OF PUBLICATION AND IS SUBJECT TO CHANGE WITHOUT NOTICE. CISCO RESERVES
THE RIGHT TO CHANGE OR UPDATE ALERTS AT ANY TIME.
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