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AUSCERT External Security Bulletin Redistribution
Cisco Virtual Topology System TCP Connection Functionality
Denial of Service Vulnerability
27 November 2015
AusCERT Security Bulletin Summary
Product: Cisco Virtual Topology System
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2015-6377
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Cisco Security Advisory
Cisco Virtual Topology System TCP Connection Functionality Denial of Service
2015 November 23 16:00 GMT
Base - 5.0
No workarounds available
Cisco Bug IDs:
A vulnerability in TCP connection handling by Cisco Virtual Topology System
(VTS) devices could allow an unauthenticated, remote attacker to disable TCP
ports and cause a denial of service (DoS) condition due to high CPU and memory
The vulnerability is due to a lack of rate limiting in the TCP listen
application. An attacker could exploit this vulnerability by sending a crafted
TCP traffic stream in which specific types of TCP packets are flooded to an
affected device. An example could be a TCP packet stream in which the TCP FIN
bit is set in all the TCP packets. An exploit could allow the attacker to
cause certain TCP listen ports to stop accepting incoming connections for a
period of time or until the device is restarted. In addition, during the DoS
attack, system resources such as CPU and memory can be exhausted.
Cisco has not released software updates that address this vulnerability. There
are no workarounds that mitigate this vulnerability.
This advisory is available at the following link:
Cisco Virtual Topology System (VTS) Releases 2.0(0) and 2.0(1) are vulnerable.
Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by this
There are no workarounds that mitigate this vulnerability.
When considering software upgrades, customers are advised to consult the Cisco
Security Advisories and Responses archive at http://www.cisco.com/go/psirt and
review subsequent advisories to determine exposure and a complete upgrade
In all cases, customers should ensure that the devices to upgrade contain
sufficient memory and confirm that current hardware and software
configurations will continue to be supported properly by the new release. If
the information is not clear, customers are advised to contact the Cisco
Technical Assistance Center (TAC) or their contracted maintenance providers.
Exploitation and Public Announcements
The Cisco Product Security Incident Response Team (PSIRT) is not aware of any
public announcements or malicious use of the vulnerability that is described
in this advisory.
Version Description Section Status Date
1.0 Initial public release. Final 2015-November-23
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF
GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS
LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO
CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
A standalone copy or paraphrase of the text of this document that omits the
distribution URL is an uncontrolled copy and may lack important information or
contain factual errors. The information in this document is intended for end
users of Cisco products.
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