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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2022.4818 Cisco IOS XE Software IPv6 VPN over MPLS Denial of Service Vulnerability 29 September 2022 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Cisco IOS XE Publisher: Cisco Systems Operating System: Cisco Resolution: Patch/Upgrade CVE Names: CVE-2022-20915 Original Bulletin: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-6vpe-dos-tJBtf5Zv Comment: CVSS (Max): 7.4 CVE-2022-20915 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H) CVSS Source: Cisco Systems Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H - --------------------------BEGIN INCLUDED TEXT-------------------- Cisco IOS XE Software IPv6 VPN over MPLS Denial of Service Vulnerability Priority: High Advisory ID: cisco-sa-iosxe-6vpe-dos-tJBtf5Zv First Published: 2022 September 28 16:00 GMT Version 1.0: Final Workarounds: Yes Cisco Bug IDs: CSCwa41184 CVE Names: CVE-2022-20915 CWEs: CWE-115 Summary o A vulnerability in the implementation of IPv6 VPN over MPLS (6VPE) with Zone-Based Firewall (ZBFW) of Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper error handling of an IPv6 packet that is forwarded from an MPLS and ZBFW-enabled interface in a 6VPE deployment. An attacker could exploit this vulnerability by sending a crafted IPv6 packet sourced from a device on the IPv6-enabled virtual routing and forwarding (VRF) interface through the affected device. A successful exploit could allow the attacker to reload the device, resulting in a DoS condition. Cisco has released software updates that address this vulnerability. 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-iosxe-6vpe-dos-tJBtf5Zv This advisory is part of the September 2022 release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2022 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication. Affected Products o Vulnerable Products This vulnerability affects Cisco devices if they are running a vulnerable release of Cisco IOS XE Software and have both 6VPE and ZBFW features enabled. For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory. Determine the Device Configuration Determine Whether IPv6 VPN Is Enabled To determine whether IPv6 VPN is enabled, issue the show running-config | include address-family vpnv6 CLI command. If there is an error or no output, IPv6 VPN is not enabled. The following output shows a device with IPv6 VPN enabled: Router# show running-config | include address-family vpnv6 address-family vpnv6 Determine Whether MPLS and ZBFW Are Enabled To determine whether MPLS and ZBFW are enabled, issue the show running-config | include interface|zone-member|mpls ip CLI command. The following output shows an interface that has both MPLS and ZBFW enabled. Router# show running-config | include interface|zone-member|mpls ip interface GigabitEthernet0/0/0 zone-member security zone_name mpls ip If both mpls ip and zone-member security are displayed on the same interface and address-family vpnv6 is configured, further verification is required. Because 6VPE is the mechanism by which the IPv4 MPLS backbone provides IPv6 VPN services, the IPv6 routing table must be investigated to confirm whether IPv6 VPN networks are being forwarded though an IPv4 MPLS backbone. For more information about 6VPE, see the MPLS Layer 3 VPNs Configuration Guide . Note : IPv6 over MPLS (6PE) configurations are not affected. Products Confirmed 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 the following Cisco products: IOS Software IOS XR Software Meraki products NX-OS Software Workarounds o There is a workaround that addresses this vulnerability. Administrators can disable ICMPv6 unreachables on the mpls ip and zone-member security enabled interface with the CLI command no ipv6 unreachables . While this workaround has been deployed and was proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment. Fixed Software o Cisco has released free software updates that address the vulnerability described in this advisory. Customers with service contracts that entitle them to regular software updates should obtain security fixes through their usual update channels. 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. The Cisco Support and Downloads page on Cisco.com provides information about licensing and downloads. This page can also display customer device support coverage for customers who use the My Devices tool. When considering software upgrades , customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories 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 Without Service Contracts 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. Cisco IOS and IOS XE Software To help customers determine their exposure to vulnerabilities in Cisco IOS and IOS XE Software, Cisco provides the Cisco Software Checker . This tool identifies any Cisco security advisories that impact a specific software release and the earliest release that fixes the vulnerabilities that are described in each advisory ("First Fixed"). If applicable, the tool also returns the earliest release that fixes all the vulnerabilities that are described in all the advisories that the Software Checker identifies ("Combined First Fixed"). To use the tool, go to the Cisco Software Checker page and follow the instructions. Alternatively, use the following form to determine whether a release is affected by any Cisco Security Advisory. To use the form, follow these steps: 1. Choose which advisories the tool will search-only this advisory, only advisories with a Critical or High Security Impact Rating (SIR) , or all advisories. 2. Enter a release number-for example, 15.9(3)M2 or 17.3.3. 3. Click Check Exploitation and Public Announcements o 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. Source o This vulnerability was found during the resolution of a Cisco TAC support case. Cisco Security Vulnerability Policy o 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. Related to This Advisory o Cisco Event Response: September 2022 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication URL o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-6vpe-dos-tJBtf5Zv Revision History o +----------+---------------------------+----------+--------+--------------+ | Version | Description | Section | Status | Date | +----------+---------------------------+----------+--------+--------------+ | 1.0 | Initial public release. | - | Final | 2022-SEP-28 | +----------+---------------------------+----------+--------+--------------+ - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. 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On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: https://auscert.org.au/gpg-key/ iQIVAwUBYzTpxMkNZI30y1K9AQgCFxAAj1jvi6NhTa9due5x/aEHUe69SC0VU/ug SY5Quar8ol4v20kKD8tNF2Uu31PSSoz3jKdNeZKK0mMEni2uZW3RmsrConakJyq6 TQV8v6mNQT9cBbiJvISYtgtTlGYUrsFDOjL2Uxacwp+zvF3B/N3P4JM5dNffDl8r f+LWcjlsYXFHcj42BZOdll9G7WOE/aZs+uXGMQBt+E/anFNip/ZZLl/6IcmBV/QX slo/phtzyAYb5XCx2aF2+3RLuXCPorYtYmvrFqB7Up51rmd+xdVVk2SetkkhPCor s46VplcmVgjjPC/csU5WuTcEcaQSk19VQLNA9QIBXwGxXP6P7uG3PO3Za2LuHDOC 3FTfxPCXuI6aGLd+Sp6sJEte6BV0Z81eStvevKWj7TDXu3MthOTC6dzJ7WZko4gg bXebNnl+Z839wYSzmfHRTAlS2IhsaERnA8//6+byqpbszRQShft5mRn5cKBGkbjr 8bAQfqnCKLwv0kaSSQCtO3pnbiyvOUbU+aUfoikJ+dh6aPj79opWzuCHPtM/3CwN fiSA5u0A+bXSM/7FGTZ4bp4EG5VI7RvZovb0bqbCChA+UZCh/OAAESPXlhq9Q5Yf uyj7DD4paKJXvMxTI0927Cp20+jVSlw59vHrmJwJ3nStsnvhqQsy1GQd39KlY8Ae CjHEWUWXalE= =RsEy -----END PGP SIGNATURE-----