IntelliShield has updated this alert to remove a Cisco Bug ID that was previously associated with the alert.
A vulnerability in the flow manager code of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause flow manager to hold UDP sessions in its table.
The vulnerability is due to not releasing memory for flows generated by TFTP UDP traffic. An attacker could exploit this vulnerability by either starting a local TFTP transaction from the device, or by requesting a TFTP file operation when the device is configured as a TFTP server. An exploit could allow the attacker to have the Cisco IOS XE software hold the flow manager sessions in a table, decreasing memory and eventually resulting in system instability or a potential system crash.
Cisco has confirmed the vulnerability in a security notice and released software updates.
At the time this alert was first published, Cisco IOS XE Software Release 3.4SG(.2) and prior were vulnerable. Later releases of Cisco IOS XE Software may also be vulnerable.
Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.
Cisco has released a security notice at the following link: CVE-2013-6704
Customers are advised to consult Cisco bug ID CSCty42686 for the most complete list of affected product versions.
An unauthenticated, remote attacker could exploit this vulnerability to cause the affected software to hold the flow manager sessions in its table. This could cause decreasing memory, resulting in system instability or a crash that would cause a denial of service (DoS) condition.
The vulnerability is due to an improper memory operation by the affected software for flows generated by TFTP UDP traffic.
An attacker could exploit this vulnerability by either starting a local TFTP transaction from the device, or by requesting a TFTP file operation when the device is configured as a TFTP server. An exploit could allow the attacker to have the affected software hold the flow manager sessions in a table, decreasing memory and eventually resulting in system instability or a potential system crash, resulting in a DoS condition.
Administrators are advised to apply the appropriate updates
Administrators are advised to allow only trusted users to have network access.
Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
Administrators are advised to monitor affected systems.
Cisco customers with active contracts should contact their Cisco support team for assistance in upgrading to a software version that includes fixes for this vulnerability. Cisco customers without contracts may contact the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via email at email@example.com for assistance.
Version 1, December 3, 2013, 5:41 PM: Cisco IOS XE Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service condition. Updates are available.
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.