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             AUSCERT External Security Bulletin Redistribution

                               ESB-2015.1664
  Cisco IOS XR MPLS LDP Packet Processing Denial of Service Vulnerability
                               26 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 -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2015-4223  

Original Bulletin: 
   http://tools.cisco.com/security/center/viewAlert.x?alertId=39509

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Vulnerability Alert

Cisco IOS XR MPLS LDP Packet Processing Denial of Service Vulnerability

Threat Type: CWE-399: Resource Management Errors

IntelliShield ID: 39509

Version: 1

First Published: 2015 June 24 18:24 GMT

Last Published: 2015 June 24 18:24 GMT

Port: Not available

CVE: CVE-2015-4223

Urgency: Unlikely Use

Credibility: Confirmed

Severity: Mild Damage

CVSS Base: 4.3

CVSS Version 2.0

CVSS Temporal: 3.6

Version Summary: Cisco IOS XR contains a vulnerability that could allow an 
unauthenticated, remote attacker to cause a denial of service condition. 
Updates are available.

Description

A vulnerability in the Multiprotocol Label Switching (MPLS) Label Distribution
Protocol (LDP) packet processing feature of Cisco IOS XR could allow an 
unauthenticated, remote attacker to cause a reload of the MPLS LDP process on
the affected device.

The vulnerability is due to improper processing of crafted MPLS LDP packets. 
An attacker could exploit this vulnerability by sending crafted MPLS LDP 
packets to be processed by an affected device. An exploit could allow the 
attacker to cause a reload of the MPLS LDP process on the affected device.

Cisco has confirmed the vulnerability and released software updates.

Warning Indicators

At the time this alert was first published, Cisco IOS XR Software Release 
5.1.3 was vulnerable. Later releases of Cisco IOS XR Software may also be 
vulnerable.

IntelliShield Analysis

To exploit this vulnerability, an attacker may need to acquire additional 
information about the targeted device, such as whether the device is 
configured to process MPLS LDP packets. A device configured to process MPLS 
LDP packets is required for 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 CSCuu77478 for registered users, which contains 
additional details and an up-to-date list of affected product versions.

Impact

An unauthenticated, remote attacker could exploit the vulnerability to cause 
the MPLS LDP process on the affected device to reload, resulting in a denial 
of service (DoS) condition.

Technical Information

The vulnerability is due to improper processing of crafted MPLS LDP packets by
an affected device.

An unauthenticated, remote attacker could exploit this vulnerability by 
sending crafted MPLS LDP packets to a targeted device. An exploit could allow
the attacker to cause the MPLS LDP process on the device to reload, 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 can help protect affected systems from external attacks by 
using a solid firewall strategy.

Administrators may consider using IP-based access control lists (ACLs) to 
allow only trusted systems to access the affected 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 .3

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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