Cisco Security Advisory
Cisco ASR 1000 Series Aggregation Services Routers Fragmented Packet Denial of Service Vulnerability
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AV:N/AC:L/Au:N/C:N/I:N/A:C/E:F/RL:OF/RC:C
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A vulnerability in the code handling the reassembly of fragmented IP version 4 (IPv4) or IP version 6 (IPv6) packets of Cisco IOS XE Software for Cisco ASR 1000 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to cause a crash of the Embedded Services Processor (ESP) processing the packet.
The vulnerability is due to improper processing of crafted, fragmented packets. An attacker could exploit this vulnerability by sending a crafted sequence of fragmented packets. An exploit could allow the attacker to cause a reload of the affected platform.
Cisco has released software updates that address this vulnerability.
There are no workarounds to mitigate this vulnerability.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20150730-asr1k
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Vulnerable Products
All Cisco ASR 1000 Series Aggregation Services Routers models are affected by this vulnerability when running an affected version of Cisco IOS XE Software. This vulnerability does not depend on any specific combination of ESP and Route Processor (RP) installed on the chassis. Any combination of ESP and RP is affected.Products Confirmed Not Vulnerable
Only Cisco ASR 1000 Series Aggregation Services Routers running an affected version of Cisco IOS XE Software are affected by this vulnerability.
Cisco 4000 Series Integrated Services Routers and Cisco Cloud Services Router 1000V Series are not affected by this vulnerability.
No other Cisco devices running Cisco IOS XE Software are affected by this vulnerability.
Cisco IOS Software is not affected by this vulnerability.
Cisco IOS XR Software is not affected by this vulnerability.
Cisco NX-OS Software is not affected by this vulnerability.
No other Cisco products are currently known to be affected by this vulnerability.
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A vulnerability in the code handling the reassembly of fragmented IP version 4 (IPv4) or IP version 6 (IPv6) packets of Cisco IOS XE Software for Cisco ASR 1000 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to cause a crash of the Embedded Services Processor (ESP) processing the packet.
The vulnerability is due to improper processing of crafted, fragmented packets. An attacker could exploit this vulnerability by sending a crafted sequence of fragmented packets. An exploit could allow the attacker to cause a reload of the affected platform.
This vulnerability can be triggered by IPv4 or IPv6 crafted, fragmented packets destined to the device itself. It cannot be triggered by transit traffic.
This vulnerability could be repeatedly exploited to cause an extended DoS condition.
This vulnerability is documented in Cisco bug ID CSCtd72617 (registered customers only), and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2015-4291.
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There are no workarounds for this vulnerability.
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When considering software upgrades, customers are advised to consult the Cisco Security Advisories, Responses, and Alerts archive at http://www.cisco.com/go/psirt and review subsequent advisories to determine exposure and a complete upgrade solution.
This vulnerability has been fixed in the following Cisco IOS XE Software versions:
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 XE Software Train First Fixed Release 2.1 Vulnerable; migrate to 2.5.1 or later. (1) 2.2 Vulnerable; migrate to 2.5.1 or later. (1) 2.3 Vulnerable; migrate to 2.5.1 or later. (1) 2.4 2.4.3 (1) 2.5 2.5.1 (1) 2.6 Not vulnerable Any 3.x train. Not vulnerable (2)
Notes
1. Cisco encourages customers migrating to a Cisco IOS XE Software train different from the one currently running on the device to select one of the Cisco IOS XE Software extended support trains including, but not limited to, Cisco IOS XE Software trains 3.4S, 3.7S, and 3.10S. Consult your support provider for the most appropriate software train to migrate to, based on the specific device hardware configuration and feature requirements.
2. No Cisco IOS XE Software trains with a major version number starting with the number 3 (such as 3.xS, 3.xSE, and 3.xSQ) are affected by the vulnerability described in this Cisco Security Advisory.
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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.
Cisco PSIRT is aware of disruption for some Cisco customers with Cisco ASR 1000 Series Aggregation Services Routers devices affected by this vulnerability. Traffic causing the disruption was isolated to a specific source IPv4 address. Cisco has engaged the owner of that address and determined that the traffic was sent with no malicious intent. Cisco strongly recommends that customers upgrade to a fixed Cisco IOS XE Software release to remediate this issue.This vulnerability was found internally by Cisco.
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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 LessRevision 1.0 2015-July-30 Initial public release.
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