Cisco Security Advisory
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AV:N/AC:L/Au:N/C:N/I:N/A:P/E:F/RL:OF/RC:C
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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.
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.
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Cisco has released bug ID CSCuo37957 for registered users, which contains additional details and an up-to-date list of affected product versions.
Vulnerable Products
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.Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by these vulnerabilities.
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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.
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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.
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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.
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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.
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Show LessVersion Description Section Status Date 1.0 Cisco IOS-XE Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service condition. Updates are available. NA Final 2015-Jul-29
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