A vulnerability in the Session Initiation Protocol (SIP) library of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to trigger a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to insufficient sanity checks on received SIP messages. An attacker could exploit this vulnerability by sending crafted SIP messages to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service condition. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is available at the following link: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sip-Cv28sQw2 This advisory is part of the June 3, 2020, release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication, which includes 23 Cisco Security Advisories that describe 25 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: June 2020 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.
A vulnerability in the Session Initiation Protocol (SIP) library of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to trigger a reload of an affected device, resulting in a denial of service (DoS) condition.
The vulnerability is due to insufficient sanity checks on received SIP messages. An attacker could exploit this vulnerability by sending crafted SIP messages to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service condition.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sip-Cv28sQw2
This advisory is part of the June 3, 2020, release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication, which includes 23 Cisco Security Advisories that describe 25 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: June 2020 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.
This vulnerability affects Cisco routers that are running a vulnerable release of Cisco IOS or IOS XE Software with any of the following features configured:
For information about which Cisco IOS and Cisco IOS XE releases are vulnerable, see the Fixed Software section of this advisory.
To determine whether a device is vulnerable, administrators can use the show processes | include CCSIP_SPI command in the CLI and look for the presence of the CCSIP_SPI_CONTRO process. The following example shows the output of the show processes | include CCSIP_SPI command on a device that has at least one of the affected features enabled and is vulnerable:
Router#show processes | include CCSIP_SPI 671 Mwe 561F108FE8BA 10 11 909234584/240000 0 CCSIP_SPI_CONTRO
Empty output of this command indicates that none of the affected features are enabled and the device is not vulnerable.
Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect Cisco IOS XR Software or Cisco NX-OS Software.
There are no workarounds that address this vulnerability.
However, customers who do not use any SIP features but who have other voice-related features enabled, which automatically enables the SIP processes in Cisco IOS and IOS XE Software releases prior to Release 16.11, can shut down the SIP ports by issuing the following commands in global configuration mode:Router(config)#sip-ua Router(config-sip-ua)#no transport udp Router(config-sip-ua)#no transport tcp Router(config-sip-ua)#no transport tcp tls
Alternatively, customers can block traffic targeted to the designated SIP ports using infrastructure access control lists (iACLs). Using iACLs is a network security best practice and should be considered as a long-term addition to good network security as well as a mitigation for this specific issue. To help protect all devices with IP addresses in the infrastructure IP address range, customers are advised to include the following iACL example as part of the deployed iACL:
!--- !--- Feature: SIP !--- !--- Permit trusted SIP sources. !--- !--- Permit additional Layer 3 and Layer 4 traffic destined for infrastructure !--- address space as dictated by existing security policies and configurations. !--- Permit/deny to infrastructure IP addresses in accordance with security policy. !--- !--- Deny SIP traffic from all other sources destined !--- to infrastructure addresses !---
access-list 150 deny udp any INFRASTRUCTURE_ADDRESSES WILDCARD eq 5060 access-list 150 deny tcp any INFRASTRUCTURE_ADDRESSES WILDCARD eq 5060 access-list 150 deny tcp any INFRASTRUCTURE_ADDRESSES WILDCARD eq 5061
!--- !--- Permit/deny all other Layer 3 and Layer 4 traffic in !--- accordance with existing security policies and !--- configurations. Permit all other traffic to transit the !--- device. !---
access-list 150 permit ip any any
!--- !--- Apply access-list to all interfaces (only one example !--- shown) !---
interface GigabitEthernet 2/0 ip access-group 150 in
For further guidelines and recommendations for deployment techniques for iACLs, see the white paper Protecting Your Core: Infrastructure Protection Access Control Lists and the Cisco Guide to Harden Cisco IOS Devices.
Note: By default, SIP uses UDP and TCP port 5060 for SIP and TCP port 5061 for SIP over TLS. However, these ports are user-configurable using the listen-port non-secure
Cisco has released free software updates that address the vulnerability described in this advisory. Customers may only install and expect support for software versions and feature sets for which they have purchased a license. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.html
Additionally, customers may only download software for which they have a valid license, procured from Cisco directly, or through a Cisco authorized reseller or partner. In most cases this will be a maintenance upgrade to software that was previously purchased. Free security software updates do not entitle customers to a new software license, additional software feature sets, or major revision upgrades.
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.
Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco TAC:
https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html
Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade.
To help customers determine their exposure to vulnerabilities in Cisco IOS and IOS XE Software, Cisco provides the Cisco Software Checker to identify any Cisco Security Advisories that impact a specific software release and the earliest release that fixes the vulnerabilities described in each advisory (“First Fixed”). If applicable, the tool also returns the earliest release that fixes all the vulnerabilities described in all the advisories identified (“Combined First Fixed”).
Customers can use the Cisco Software Checker to search advisories in the following ways:
After initiating a search, customers can customize the search to include all Cisco Security Advisories, a specific advisory, or all advisories in the most recent bundled publication.
Customers can also use the following form to determine whether a release is affected by any Cisco Security Advisory by entering a Cisco IOS or IOS XE Software release-for example, 15.1(4)M2 or 3.13.8S:
By default, the Cisco Software Checker includes results only for vulnerabilities that have a Critical or High Security Impact Rating (SIR). To include results for Medium SIR vulnerabilities, customers can use the Cisco Software Checker on Cisco.com and check the Medium check box in the drop-down list under Impact Rating when customizing a search.
For a mapping of Cisco IOS XE Software releases to Cisco IOS Software releases, refer to the Cisco IOS XE 2 Release Notes, Cisco IOS XE 3S Release Notes, or Cisco IOS XE 3SG Release Notes, depending on the Cisco IOS XE Software release.
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.
This vulnerability was found by Puspalatha S of Cisco during internal security testing.
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 |
|---|---|---|---|---|
| 1.0 | Initial public release. | - | Final | 2020-June-03 |
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