ESB-2017.2249 - [Cisco] Cisco IOS and Cisco IOS XE: Denial of service - Remote/unauthenticated 2017-09-07

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             AUSCERT External Security Bulletin Redistribution

                               ESB-2017.2249
         Cisco IOS and Cisco IOS XE Software UDP Packet Processing
                      Denial of Service Vulnerability
                             7 September 2017

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Cisco IOS and Cisco IOS XE
Publisher:         Cisco Systems
Operating System:  Cisco
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2017-6627  

Original Bulletin: 
   https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170906-ios-udp

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Cisco IOS and Cisco IOS XE Software UDP Packet Processing Denial of Service 
Vulnerability

Medium

Advisory ID: cisco-sa-20170906-ios-udp

First Published: 2017 September 6 16:00 GMT

Version 1.0: Final

Workarounds: Yes

Cisco Bug IDs:

CSCup10024

CSCva55744

CSCva95506

CVSS Score:

Base 5.3

Base 5.3 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:X/RL:X/RC:X

CVE-2017-6627

CWE-399

Summary

A vulnerability in the UDP processing code of Cisco IOS and Cisco IOS XE 
Software could allow an unauthenticated, remote attacker to cause the input 
queue of an affected system to hold UDP packets, causing an interface queue 
wedge and a denial of service (DoS) condition.

The vulnerability is due to Cisco IOS Software application changes that create
UDP sockets and leave the sockets idle without closing them. An attacker could
exploit this vulnerability by sending UDP packets with a destination port of 0
to an affected device. A successful exploit could allow the attacker to cause
UDP packets to be held in the input interfaces queue, resulting in a DoS 
condition. The input interface queue will stop holding UDP packets when it 
receives 250 packets.

There are workarounds that address this vulnerability.

This advisory is available at the following link:

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170906-ios-udp

Affected Products

Vulnerable Products

This vulnerability affects Cisco IOS and Cisco IOS XE Software. For 
information about affected software releases, consult the Cisco bug ID(s) at 
the top of this advisory.

Products Confirmed Not Vulnerable

No other Cisco products are currently known to be affected by this 
vulnerability.

Workarounds

To work around this vulnerability, administrators can set a maximum hold queue
value that is greater than 250 for all device interfaces. The following 
example shows how to set the value to 350 by using the hold queue in interface
configuration command:

Router# configure terminal

Router(config)# interface gigabitEthernet 1

Router(config-if)# hold-queue 350 in

Administrators can also configure an access-control list (ACL) that blocks UDP
packets with a destination port of 0 and apply the ACL to all device 
interfaces, for example:

Extended IP access list 180

    10 deny udp any any eq 0

Fixed Software

For information about fixed software releases, consult the Cisco bug ID(s) at
the top of this advisory.

When considering software upgrades, customers are advised to regularly consult
the advisories for Cisco products, which are available from the Cisco Security
Advisories and Alerts page, to determine exposure and a complete upgrade 
solution.

In all cases, customers should ensure that the devices to be upgraded 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.

URL

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170906-ios-udp

Revision History

Version 	Description 		Section Status 	Date

1.0 		Initial public release. -	Final 	2017-September-06

LEGAL DISCLAIMER

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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