Cisco Security Advisory
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On August 6, 2018, the Vulnerability Coordination team of the National Cyber Security Centre of Finland (NCSC-FI) and the CERT Coordination Center (CERT/CC) disclosed vulnerabilities in the TCP stacks that are used by the Linux and FreeBSD kernels. These vulnerabilities are publicly known as SegmentSmack.
The vulnerabilities could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. An attack could be executed by using low transfer rates of TCP packets, unlike typical distributed denial of service (DDoS) attacks.
The vulnerabilities are due to inefficient TCP reassembly algorithms in the TCP stacks that are used by the affected kernels. Linux Kernel Versions 4.9 and later and all supported versions of the FreeBSD kernel are known to be affected by these vulnerabilities.
An attacker could exploit these vulnerabilities by sending a stream of packets that are designed to trigger the issue in an established TCP session with an affected device. A sustained DoS condition requires the attacker to maintain a continuous stream of malicious traffic. Due to the required use of an established session, an attack cannot be performed using spoofed IP addresses.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180824-linux-tcp
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Cisco investigated its product line to determine which products and services may be affected by these vulnerabilities.
The “Vulnerable Products” section of this advisory includes Cisco bug IDs for each affected product or service. The bugs are accessible through the Cisco Bug Search Tool and contain additional platform-specific information, including workarounds (if available) and fixed software releases.
Any product or service not listed in the “Vulnerable Products” section of this advisory is to be considered not vulnerable.
Vulnerable Products
The following table lists Cisco products that are affected by the Linux Kernel vulnerability that is described in this advisory:
Product Cisco Bug ID Fixed Release Availability Network and Content Security Devices Cisco Threat Grid Appliance M5 CSCvk69486 2.5 (Oct-2018) Routing and Switching - Enterprise and Service Provider Cisco DNA Center CSCvm34581 1.3 (Apr-2019) Cisco Network Assurance Engine CSCvm34702 3.0(0) (Nov-2018) Voice and Unified Communications Devices Cisco Webex Hybrid Data Security Node CSCvm49456 Cisco will update affected systems (Nov-2018) Cisco Webex Video Mesh Node CSCvm48163 Cisco will update affected systems (Nov-2018) Video, Streaming, TelePresence, and Transcoding Devices Cisco Expressway Series CSCvk74922 x12.5 (Jan-2019) Cisco Meeting Management CSCvk69487 1.1.0.27 (Sept-2018) Cisco TelePresence Conductor CSCvk75754 4.3.4 MR (Nov-2018) Cisco TelePresence Video Communication Server (VCS) CSCvk74922 x12.5 (Jan-2019) The following table lists Cisco products that are affected by the FreeBSD vulnerability that is described in this advisory:
Product Cisco Bug ID Fixed Release Availability Network and Content Security Devices Cisco Content Security Management Appliance (SMA) CSCvk74266 12.0.0 (Nov-2018) Cisco Email Security Appliance (ESA) CSCvk74109 11.0.3 (Oct-2018)
12.0.0 (Nov-2018)Cisco Web Security Appliance (WSA) CSCvk74112 10.1.4 (Sept-2018)
10.5.3 (Oct-2018)
11.5.2 (Nov-2018)
Video, Streaming, TelePresence, and Transcoding Devices Cisco TelePresence MCU 5300 Series, MSE 8510 CSCvk74254 4.5(1.98) (Oct-2018) Cisco TelePresence MCU MSE 8420 CSCvk74254 No fix expected - End of life Cisco TelePresence Server 7010 and MSE 8710 CSCvk74256 4.4(1.27) (Dec-2018) Cisco TelePresence Server on Multiparty Media 310, 320 and 820 CSCvk74256 4.4(1.27) (Dec-2018)
Products Confirmed Not Vulnerable
Only products and services listed in the “Vulnerable Products” section of this advisory are known to be affected by this vulnerability.
Network and Content Security Devices
Cisco has confirmed that this vulnerability does not affect the following products and services:- Cisco Firepower Management Center
Video, Streaming, TelePresence, and Transcoding Devices- Cisco TelePresence MCU 4200 Series and 4500 Series
- Cisco TelePresence Advanced Media Gateway Series
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Any workarounds will be documented in the product-specific Cisco bugs, which are identified in the “Vulnerable Products” section of this advisory.
It is important to note that exploitation of these vulnerabilities requires an attacker to establish a TCP three-way handshake with an open TCP port on an affected device. Customers are therefore advised to use an external firewall to allow only explicitly trusted source IP addresses to connect to open TCP ports on affected devices.
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For information about fixed software releases, consult the Cisco bugs identified in the “Vulnerable Products” section 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 TAC or their contracted maintenance providers.
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The Cisco Product Security Incident Response Team (PSIRT) is not aware of any malicious use of the vulnerabilities that are described in this advisory.
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These vulnerabilities were reported by Juha-Matti Tilli, of the Aalto University Department of Communications and Networking, and Nokia Bell Labs.
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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 1.7 Updated information about fixed release availability. Removed references to ongoing investigation. Summary, Affected Products, Vulnerable Products Final 2018-November-06 1.6 Updated the lists of products under investigation and vulnerable products. Affected Products, Vulnerable Products Interim 2018-September-17 1.5 Updated the lists of products under investigation. Moved Firepower Management Center to the products confirmed not vulnerable as after further evaluation, no publicly available software releases were found to be vulnerable. Affected Products, Vulnerable Products, Products Confirmed Not Vulnerable Interim 2018-September-13 1.4 Updated the lists of products under investigation and vulnerable products. Updated information about fixed release availability. Affected Products, Vulnerable Products Interim 2018-September-06 1.3 Updated the lists of products under investigation, vulnerable products, and products confirmed not vulnerable. Updated information about fixed release availability. Affected Products, Vulnerable Products, Products Confirmed Not Vulnerable Interim 2018-September-04 1.2 Updated information about fixed release availability. Vulnerable Products Interim 2018-August-30 1.1 Updated the lists of products under investigation and products confirmed not vulnerable. Updated information about fixed release availability. Affected Products, Vulnerable Products, Products Confirmed Not Vulnerable Interim 2018-August-29 1.0 Initial public release. — Interim 2018-August-24
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