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 native passthrough FTP functionality of the Cisco Web Security Appliance (WSA) could allow an unauthenticated, remote attacker to cause a partial denial of service (DoS) condition due to high CPU utilization.
The vulnerability occurs when the FTP client terminates the FTP control connection when the data transfer is complete. An attacker could exploit this vulnerability by initiating FTP connections through the WSA. An exploit could allow the attacker to cause high CPU utilization of the Cisco WSA proxy process, causing a partial DoS condition. The attacker's choice of FTP client and how that client closes the FTP control connection will affect the attacker's ability to exploit this vulnerability.
Cisco has released software updates that address this vulnerability. There is a workaround that mitigates this vulnerability.
This advisory is available at the following link: http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151130-wsa
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This vulnerability exists only if native FTP is configured on the WSA. To disable native FTP on the WSA by using the GUI, navigate to Security Services > FTP Proxy and then disable the FTP Proxy setting.
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When considering software upgrades, customers are advised to consult the Cisco Security Advisories and Responses archive at http://www.cisco.com/go/psirt and review subsequent advisories to determine exposure and a complete upgrade solution.
In all cases, customers should ensure that the devices to upgrade 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.
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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 2.1 Updated information about vulnerable products and added a workaround. Affected Products; Workarounds Final 2015-December-07 2.0 Removed content from the Workarounds section. Workarounds Final 2015-December-01 1.0 Initial public release. — Final 2015-November-30
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