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AUSCERT External Security Bulletin Redistribution
ESB-2015.2464
Cisco Nexus 9000 Series Switches Reserved VLAN Number Vulnerability
22 September 2015
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AusCERT Security Bulletin Summary
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Product: Cisco Nexus 9000 Series Switches
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Mitigation
CVE Names: CVE-2015-6295
Original Bulletin:
http://tools.cisco.com/security/center/viewAlert.x?alertId=40990
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Vulnerability Alert
Cisco Nexus 9000 Series Switches Reserved VLAN Number Vulnerability
Threat Type: CWE-399: Resource Management Errors
IntelliShield ID: 40990
Version: 1
First Published: 2015 September 16 16:08 GMT
Last Published: 2015 September 16 16:08 GMT
Port: Not available
CVE: CVE-2015-6295
Urgency: Unlikely Use
Credibility: Confirmed
Severity: Mild Damage
CVSS Base: 4.8
CVSS Temporal: 4.6
Version Summary: Cisco Nexus 9000 Series Switches contain a vulnerability that
could allow an unauthenticated, adjacent attacker to cause a denial of service
condition. Updates are not available.
Description
A vulnerability in the handling of incoming Layer 2 packets tagged with a
Cisco Nexus 9000 Series Switch (N9K) reserved VLAN number could allow an
unauthenticated, adjacent attacker to cause a partial denial of service (DoS)
condition due to increased CPU utilization and possible control plane
instability. In addition, Layer 2 packets, which should be dropped by the
switch, may be incorrectly forwarded to the connected interfaces.
The vulnerability is due to lack of validation of the VLAN number in the Layer
2 packet. An attacker could exploit this vulnerability by sending a crafted
Layer 2 packet tagged with an N9K reserved VLAN number. An exploit could allow
the attacker to cause a partial DoS condition due to increased CPU utilization
and possible control plane instability. In addition, this packet should be
dropped by the N9K, but could be forwarded to the attached networks.
Cisco has confirmed the vulnerability; however, updates are not available.
Warning Indicators
At the time this alert was first published, Cisco Nexus 9000 Series Software
Releases 6.1(2)I3(4) and 7.0(3)I1(1) were vulnerable. Later releases may also
be affected.
IntelliShield Analysis
To exploit the vulnerability, an unauthenticated attacker would need access to
the local network. This restriction reduces the potential for exploitation.
Vendor Announcements
Cisco has released bug ID CSCuw13560 for registered users, which contains
additional details and an up-to-date list of affected product versions.
Impact
An unauthenticated, adjacent attacker could exploit this vulnerability to
cause a DoS condition. A successful exploit may also impact confidentiality
due to errors in handling network packets.
Technical Information
The vulnerability is due to lack of validation of the VLAN number in the Layer
2 packet.
An unauthenticated, adjacent attacker could exploit this vulnerability by
sending a crafted Layer 2 packet tagged with an N9K reserved VLAN number. An
exploit could allow the attacker to cause a DoS condition due to increased CPU
and control plane instability. If the Layer 2 packet is not dropped by the
N9K, it could also be forwarded to the attached networks.
Safeguards
Administrators are advised to contact the vendor regarding future updates and
releases.
Administrators are advised to monitor affected systems.
Administrators are advised to change the reserved VLAN range so that it does
not conflict with incoming traffic.
Patches/Software
Updates are not available.
Alert History
Initial Release
Product Sets
The security vulnerability applies to the following combinations of products.
Primary Products:
Cisco Cisco NX-OS Software for Nexus 9000 Series 7.0(3)I1(1), 6.1(2)I3(4)
Associated Products:
N/A
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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