Cisco Security Advisory
Cisco IOS and Cisco IOS XE Software UDP Packet Processing Denial of Service Vulnerability
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:
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.
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
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.
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.
To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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
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