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://sec.cloudapps.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

• In March 2022, the Cisco Product Security Incident Response Team (PSIRT) became aware of additional attempted exploitation of this vulnerability in the wild. Cisco continues to strongly recommend that customers upgrade to a fixed software release to remediate this vulnerability.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170906-ios-udp

Revision History

• Version	Description	Section	Status	Date
  1.2	Updated exploitation information.	Exploitation and Public Announcements	Final	2022-DEC-16
  1.1	Corrected the list of Cisco bug IDs.	-	Final	2017-SEP-07
  1.0	Initial public release.	-	Final	2017-SEP-06

  Show Less