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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2019.0083 Cisco IOS and IOS XE Software TCP Denial of Service Vulnerability 10 January 2019 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Cisco IOS Cisco IOS XE Publisher: Cisco Systems Operating System: Cisco Impact/Access: Denial of Service -- Remote/Unauthenticated Resolution: Patch/Upgrade CVE Names: CVE-2018-0282 Original Bulletin: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190109-tcp - --------------------------BEGIN INCLUDED TEXT-------------------- Cisco IOS and IOS XE Software TCP Denial of Service Vulnerability Importance: Medium Advisory ID: cisco-sa-20190109-tcp First Published: 2019 January 9 16:00 GMT Version 1.0: Final Workarounds: No workarounds available Cisco Bug IDs: CSCvg39082 CVE-2018-0282 CWE-371 CVSS Score: Base 6.8 CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X Summary o A vulnerability in the TCP socket code of Cisco IOS and IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to a state condition between the socket state and the transmission control block (TCB) state. While this vulnerability potentially affects all TCP applications, the only affected application observed so far is the HTTP server. An attacker could exploit this vulnerability by sending specific HTTP requests at a sustained rate to a reachable IP address of the affected software. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition on an affected device. 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-20190109-tcp Affected Products o Vulnerable Products This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS or IOS XE Software if the HTTP Server feature is enabled. The default state of the HTTP Server feature is version-dependent. For information about which software releases are vulnerable, see the Fixed Software section of this advisory. Assessing the HTTP Server Configuration To determine whether the HTTP Server feature is enabled for a device, administrators can log in to the device and use the show running-config | include http (secure|server) command in the CLI to check for the presence of the ip http server command or the ip http secure-server command in the global configuration. If either command is present and configured, the HTTP Server feature is enabled for the device. The following example shows the output of the show running-config | include http (secure|server) command for a router that has the HTTP Server feature enabled: Router# show running-config | include http (secure|server) ip http server ip http secure-server Determining the Cisco IOS Software Release To determine which Cisco IOS Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and then refer to the system banner that appears. If the device is running Cisco IOS Software, the system banner displays text similar to Cisco Internetwork Operating System Software or Cisco IOS Software. The banner also displays the installed image name in parentheses, followed by the Cisco IOS Software release number and release name. Some Cisco devices do not support the show version command or may provide different output. The following example shows the output of the command for a device that is running Cisco IOS Software Release 15.5(2)T1 and has an installed image name of C2951-UNIVERSALK9-M: Router> show version Cisco IOS Software, C2951 Software (C2951-UNIVERSALK9-M), Version 15.5(2)T1, RELEASE SOFTWARE (fc1) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2015 by Cisco Systems, Inc. Compiled Mon 22-Jun-15 09:32 by prod_rel_team . . . For information about the naming and numbering conventions for Cisco IOS Software releases, see the Cisco IOS and NX-OS Software Reference Guide. Determining the Cisco IOS XE Software Release To determine which Cisco IOS XE Software release is running on a device, administrators can log in to the device, use the show version command in the CLI, and then refer to the system banner that appears. If the device is running Cisco IOS XE Software, the system banner displays Cisco IOS Software, Cisco IOS XE Software, or similar text. The following example shows the output of the command for a device that is running Cisco IOS XE Software Release 16.2.1 and has an installed image name of CAT3K_CAA-UNIVERSALK9-M: ios-xe-device# show version Cisco IOS Software, Catalyst L3 Switch Software (CAT3K_CAA-UNIVERSALK9-M), Version Denali 16.2.1, RELEASE SOFTWARE (fc1) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2016 by Cisco Systems, Inc. Compiled Sun 27-Mar-16 21:47 by mcpre . . . For information about the naming and numbering conventions for Cisco IOS XE Software releases, see the Cisco IOS and NX-OS Software Reference Guide. Products Confirmed Not Vulnerable Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability. Details o For this vulnerability to be exploited, a large number of TCP sessions would have to be set up/torn down to the affected device. Controlling HTTP/ HTTPS access to the device will limit the likelihood of an exploit of this vulnerability. Indicators of Compromise o Prior to the crash, a message similar to the following will appear, indicating an issue with the HTTP CORE process: %TCP-2-INVALIDTCB: Invalid TCB pointer: 0x3CBC2DF0 -Process= "HTTP CORE", ipl= 0, pid= 334 Workarounds o There are no workarounds that address this vulnerability. Administrators who do not use the web UI can mitigate this vulnerability by disabling the HTTP Server feature on an affected device. To disable the feature, use the no ip http server and no ip http secure-server commands in the CLI. Limiting access to the HTTP server to trusted networks will limit exposure to this vulnerability. The following example shows how to allow remote access to the HTTP server from the trusted 192.168.0.0/24 network: ! ip http access-class 75 ip http secure-server ! access-list 75 permit 192.168.0.0 0.0.0.255 access-list 75 deny any ! Note: In newer versions of Cisco IOS and IOS XE Software, to apply the access list use the ip http access-class ipv4 75 command for the previous example. Fixed Software o 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. Cisco IOS and IOS XE Software To help customers determine their exposure to vulnerabilities in Cisco IOS and IOS XE Software, Cisco provides a tool, the Cisco IOS Software Checker, that identifies 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 this tool to perform the following tasks: - Initiate a search by choosing one or more releases from a drop-down list or uploading a file from a local system for the tool to parse - Enter the output of the show version command for the tool to parse - Create a custom search by including all previously published Cisco Security Advisories, a specific advisory, or all advisories in the most recent bundled publication To determine whether a release is affected by any published Cisco Security Advisory, use the Cisco IOS Software Checker on Cisco.com or enter a Cisco IOS Software or Cisco IOS XE Software release--for example, 15.1(4)M2 or 3.13.8S--in the following field: [ ] [Check] By default, the Cisco IOS Software Checker includes results only for vulnerabilities that have a Critical or High Security Impact Rating (SIR). To include results for Medium SIR vulnerabilities, use the Cisco IOS Software Checker on Cisco.com and check the Medium check box in the Impact Rating drop-down list. 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. 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. URL o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/ cisco-sa-20190109-tcp Revision History o +----------+---------------------------+----------+--------+------------------+ | Version | Description | Section | Status | Date | +----------+---------------------------+----------+--------+------------------+ | 1.0 | Initial public release. | -- | Final | 2019-January-09 | +----------+---------------------------+----------+--------+------------------+ - --------------------------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. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. 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If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: https://www.auscert.org.au/bulletins/ =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQIVAwUBXDbRPWaOgq3Tt24GAQhyeBAArz5iwMMsQmnYRplmyCGZN5iY+5Apjj3D LOSy0Yp/Pqpm1GtYZMTT7L5cbZbTbdzcPqcV/l/T+YaTbq5wpnmSkunMe4Rveeom 7A0B8IQxclIXEHumdpUTHhf8zcwCYRrZiLFu7CQmvYLM4KTOT8XZOPqo4xClj0Gw k+svmbJB2NhkoDmt+BBm9GlLjlN5it3bqaEQ3+G8l/+8znzUQLhOoAmgjwPXXoFe YTn65PM3CLi24BKuIkbFATnvDAphqzoT8WUVJ2e0zJs7KmUEwkIkdliwINS4zZBr 8ciP9J0dPFezcNdFKKlTNIhzpQlg8aC8QsiLUB5dsEz8W3JEZ0tnXaWAF8yC58Jn EcMT32Ouh+M5IKij8u8kiPOxFhZVu4+WxjyPfd6T8rKE0ZG5nlclfgis+MbaR6pJ dxAmDD/Ltlr3obsSKZEHM9moAiiiKTuZNT51OutnOxcA0JFxtjmMavGFu2ZoM5eQ 8ScIXPrZNIcM2E/EZhWPbz0R4CoVL0CZuVXqA0lE/t8acWG0qoHJMfuZXkQfImjW Q73a0hcYKJsMc2PrEyvMmMK1pN8lWrcgJRKbRqxf7FKTUqUs38tjemtUB/ct13vR 2QBkKQUEMe4eFMMcdSl1AUqqwkqcQBt2ZeQ+UVByJe/kwro4UrtnA9DDHsP58RNl LaXU55TURek= =LCZB -----END PGP SIGNATURE-----