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AUSCERT External Security Bulletin Redistribution
Cisco IOS Software DHCPv6 Server Implementation Denial of
21 September 2015
AusCERT Security Bulletin Summary
Product: Cisco IOS Software
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2015-6297
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Cisco IOS Software DHCPv6 Server Implementation Denial of Service
Threat Type: CWE-399: Resource Management Errors
IntelliShield ID: 41060
First Published: 2015 September 18 04:41 GMT
Last Published: 2015 September 18 04:41 GMT
Port: Not available
Urgency: Unlikely Use
Severity: Mild Damage
CVSS Base: 5.0
CVSS Temporal: 4.1
Version Summary: Cisco IOS Software contains a vulnerability that could allow
an unauthenticated, remote attacker to cause a denial of service condition.
Updates are available.
A vulnerability in the DHCP version 6 (DHCPv6) server implementation of Cisco
IOS Software could allow an unauthenticated, remote attacker to cause a denial
of service (DoS) condition.
The vulnerability is due to improper handling of crafted DHCPv6 packets. An
attacker could exploit this vulnerability by sending crafted DHCPv6 packets to
be processed by the affected device. An exploit could allow the attacker to
cause a reset of an affected process.
Cisco has confirmed the vulnerability and released software updates.
At the time this alert was first published, Cisco 9000 Series Aggregation
Services Router (ASR) version 5.2.0 (Base) devices running Cisco IOS Software
were vulnerable. Other versions may also be affected.
To exploit this vulnerability a remote attacker does not need to authenticate
to pass the crafted DHCPv6 packets to the targeted device. This increases the
likelihood of a possible exploit.
Cisco indicates through the CVSS score that functional exploit code exists;
however, the code is not known to be publicly available.
Cisco has released bug ID CSCun36525 for registered users, which contains
additional details and an up-to-date list of affected product versions.
An unauthenticated, remote attacker could exploit this vulnerability to cause
an affected device to reset, resulting in a DoS condition.
The vulnerability is due to improper handling of crafted DHCPv6 packets.
An unauthenticated, remote attacker could exploit this vulnerability by
sending crafted DHCPv6 packets to an affected device. A successful exploit
could allow the attacker to cause a reset of the affected device, resulting in
a DoS condition.
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.
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 email@example.com.
The security vulnerability applies to the following combinations of products.
Cisco Cisco ASR 9000 Series Aggregation Services Routers 5.2.0(ED) Base
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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