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Vulnerability Alert

Cisco IOS XE Software TCP Segment Reassembly Denial of Service Vulnerability

 
Threat Type:CWE-399: Resource Management Errors
IntelliShield ID:31454
Version:1
First Published:2013 October 30 16:22 GMT
Last Published:2013 October 30 16:22 GMT
Port: Not available
CVE:CVE-2013-5546
Urgency:Unlikely Use
Credibility:Confirmed
Severity:Mild Damage
CVSS Base:7.8 CVSS Calculator
CVSS Version 2.0
CVSS Temporal:6.4
Related Resources:
View related Security Advisory
 
 
Version Summary:Cisco IOS XE Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service condition. Updates are available.
 
 
Description
A vulnerability in TCP segment reassembly of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition.

The vulnerability is due to improper processing of large TCP reassembled packets that are being processed by NAT and ALG features on the affected device. An attacker could exploit this vulnerability by sending a TCP packet that is large after the reassembly to traverse a vulnerable device. Only packets being handled by NAT and ALG features have a potential to cause an affected device to reload. An exploit could allow the attacker to cause a reload of the affected device, resulting in a DoS condition.

Cisco has confirmed the vulnerability in a security advisory and released software updates.
 
Warning Indicators
Cisco IOS XE Software versions prior to 3.7.3S and 3.8.1S are affected.
 
IntelliShield Analysis
Only devices performing ALG and NAT inspection are vulnerable, which may reduce the number of vulnerable systems in many environments.
 
Vendor Announcements
Cisco has released a security advisory for Cisco bug ID CSCud72509 at the following link: cisco-sa-20131030-asr1000
 
Impact
An unauthenticated, remote attacker could exploit this vulnerability to cause a vulnerable device to reload, resulting in a DoS condition.
 
Technical Information
The vulnerability is due to improper handling of fragmented packets by the Cisco IOS XE Software network address translation (NAT) and application layer gateway (ALG) inspection features.

An unauthenticated, remote attacker could exploit this vulnerability by sending malicious fragmented TCP packets within communications that transit interfaces on a vulnerable device performing NAT and ALG inspection. The reassembly of the malicious fragmented packets could cause the device to reload, resulting in a DoS condition.
 
Safeguards
Administrators are advised to apply the appropriate updates.

Administrators can help protect affected systems from external attacks by using a solid firewall strategy.

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:
CiscoCisco IOS XE Software 3.7S Base, .0, .1, .2 | 3.8S Base, .0, .1

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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