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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2015.1995 Cisco IOS-XE Fragmented Packet Resource Consumption Vulnerability 31 July 2015 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Cisco IOS-XE Software Publisher: Cisco Systems Operating System: Cisco Impact/Access: Denial of Service -- Remote/Unauthenticated Resolution: Patch/Upgrade CVE Names: CVE-2015-4293 Original Bulletin: http://tools.cisco.com/security/center/viewAlert.x?alertId=40215 - --------------------------BEGIN INCLUDED TEXT-------------------- Vulnerability Alert Cisco IOS-XE Fragmented Packet Resource Consumption Vulnerability Threat Type: CWE-399: Resource Management Errors IntelliShield ID: 40215 Version: 1 First Published: 2015 July 29 20:04 GMT Last Published: 2015 July 29 20:04 GMT Port: Not available CVE: CVE-2015-4293 Urgency: Unlikely Use Credibility: Confirmed Severity: Mild Damage CVSS Base: 5.0 CVSS Temporal: 4.1 Version Summary: Cisco IOS-XE Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service condition. Updates are available. Description A vulnerability in the packet reassembly subsystem of Cisco IOS-XE could allow an unauthenticated, remote attacker to consume CPU resources which may lead to a denial of service (DoS) condition. The vulnerability is due to an error message that is triggered to the console and the syslog when a fragmented packet cannot be properly reassembled. When an affected device fails to successfully perform reassembly, instead of silently dropping the fragments, the ATTN-3-SYNC_TIMEOUT error message may be triggered. On a device that is highly loaded, this condition may be leveraged to consume CPU resources that may be required by another process, resulting in a temporary halt of the queued process. In some situations this may lead to a drop of transit traffic. An attacker could trigger this vulnerability by sending a series of IPv4 or IPv6 fragments, that are designed to trigger the error message, directly to the affected device. Cisco IOS-XE devices rate-limit error messages to once every 60 seconds by default. Cisco has confirmed the vulnerability and released software updates. Warning Indicators At the time this alert was first published, Cisco IOS-XE Software versions 3.13S and prior were vulnerable. Later versions of Cisco IOS-XE Software may also be affected. IntelliShield Analysis To exploit the vulnerability, an attacker must send a continuous series of network packets to a targeted device. Devices that are protected by network filtering or have access restricted from untrusted networks may be at less risk of exploitation. Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available. Vendor Announcements Cisco has released bug ID CSCuo37957 for registered users, which contains additional details and an up-to-date list of affected product versions. Impact An unauthenticated, remote attacker could exploit this vulnerability to cause a targeted device to stop processing network traffic, resulting in a DoS condition. Technical Information The vulnerability is due to improper processing of fragmented packets by devices running Cisco IOS-XE Software. An unauthenticated, remote attacker could exploit the vulnerability by sending a series of malicious IPv4 or IPv6 network packets to a targeted device. The processing of message fragments could cause the device to perform logging operations resulting from the large volume of network packets, consuming additional resources and resulting in a DoS condition. Safeguards Administrators are advised to apply the appropriate updates. Administrators are advised to allow only trusted users to have network access. Administrators are advised to monitor affected systems. Patches/Software Cisco customers with active contracts can obtain updates through the Software Center at the following link: Cisco. Cisco customers without contracts can obtain upgrades by contacting the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via email at tac@cisco.com. Alert History Initial Release Product Sets The security vulnerability applies to the following combinations of products. Primary Products: Cisco Cisco IOS XE Software 2.1 .0, .1, .2 | 2.2 .1, .2, .3 | 2.3 .0, .0t, .1t, .2 | 2.4 .0, .1 | 2.5 .0, .1, .2 | 2.6 .0, .1, .2 | 3.10S .0, .0a, .1, .2, .3 | 3.11S .0, .1, .2 | 3.12S .0, .1 | 3.13S .0 Associated Products: N/A Alerts and bulletins on the Cisco Security Intelligence Operations Portal are highlighted by analysts in the Cisco Threat Operations Center and represent a subset of the comprehensive content that is available through Cisco Security IntelliShield Alert Manager Service. This customizable threat and vulnerability alert service provides security staff with access to timely, accurate, and credible information about threats and vulnerabilities that may affect their environment. LEGAL DISCLAIMER The urgency and severity ratings of this alert are not tailored to individual users; users may value alerts differently based upon their network configurations and circumstances. THE ALERT, AND INFORMATION CONTAINED THEREIN, ARE PROVIDED ON AN "AS IS" BASIS AND DO NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE ALERT, AND INFORMATION CONTAINED THEREIN, OR MATERIALS LINKED FROM THE ALERT, IS AT YOUR OWN RISK. INFORMATION IN THIS ALERT AND ANY RELATED COMMUNICATIONS IS BASED ON OUR KNOWLEDGE AT THE TIME OF PUBLICATION AND IS SUBJECT TO CHANGE WITHOUT NOTICE. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE ALERTS AT ANY TIME. - --------------------------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. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. 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On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQIVAwUBVbroZX6ZAP0PgtI9AQJbiw/+PuwChxSHHnjQU9vH2YNQ/f0B5OalY5FQ mJdU7kGUScT8HPdUXTt3oy8B4zFXaKl5MaOPN3LK3Bp8WpEQDz9sgsTQDWQFfSyF cG5FyHyjRCLuSv0DCSFT0gNNHdBDGPzhM59egqj3dt8btYGmJ5kenh+fsh0g4DMK Fj3Sx+Fy+FcpZ4FGZZqA63cmLEmc79vpGIyf04+Ua4L3yKksLuDmbTrrSK6iv7F8 5DuyuOu3nuXBbDFXcCxX0OJ0zM8zQRbHPgXe95vU1SNXAB3XavGiI9mlqKrypexC ALJjwX18I5zRJxu247B9ists+gwFq7whVT+C7xIhrKpNSkqRvz30bWfUje52ZNLb eV9tfC3K9nOx/lYtOYdX2PxW0uBH1pIRpOl/DMWDiiVLHPL7N+RkgwZkHg1bjocX 8UOyT59kMRnmmmNgX95DJ1j9dsIbw9Az04xYzWiDftWZcQrVAgERNy5UeC6Frjpt uljetiaomfOEvHW2D5oEe+iIhKQRczpugEjXTXO3FMr9CsqwkJgBkExbSLWZD+zW 35dUy0TEhex2FGTbaDaFPxcbZnIsgId0SP2JXdfRkb3UVU9WYyRs8PLZnkE3o9T/ p59Qo7T/TivEy2kgqmSs7n+SFtGY0yDMEEZ9rGu3SHumOvdc3Jp8HNp95vEAvrsE CIri11XkyJI= =MUPU -----END PGP SIGNATURE-----