Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to modify the anti-replay capabilities of IPsec on a targeted device. Updates are available.
A vulnerability in the implementation of the Cisco IOS Software Internet Key Exchange version 2 (IKEv2) protocol may cause the anti-replay capabilities of IPsec to be disabled. This issue occurs only when using the Advanced Encryption Standard Galois/Counter Mode (AES-GCM) or the AES Galois Message Authentication Code (AES-GMAC) algorithms for Phase 2 IPsec Security Associations (SAs).
The vulnerability is due to improper coding of the logic required to enable or disable the anti-replay capabilities of an IPsec Phase 2 SA. An attacker could exploit this vulnerability by sending traffic that will traverse an IPsec tunnel. An exploit could allow the attacker to replay previously sent traffic as long as the application consuming the traffic does not implement its own sequence or anti-replay checks. Neither the confidentiality nor the authentication capabilities of IPsec are affected by this vulnerability.
Cisco has confirmed the vulnerability in a security notice and released software updates.
At the time this alert was first published, Cisco IOS versions 15.3(3)M5 and prior were vulnerable. Later releases of Cisco IOS 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-2013-5548
Customers are advised to consult Cisco bug ID CSCuj47795 or the most complete list of affected product versions.
An unauthenticated, remote attacker could exploit this vulnerability to cause the anti-replay capabilities on an affected device to become disable. A successful exploit could be used to conduct further attacks.
The vulnerability is due to improper coding of the logic required to enable or disable the anti-replay capabilities of an IPsec Phase 2 SA.
An unauthenticated, remote attacker could exploit this vulnerability by sending traffic that will traverse an IPsec tunnel. An exploit could allow the attacker to replay previously sent traffic as long as the application consuming the traffic does not implement its own sequence or anti-replay checks.
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 firstname.lastname@example.org for assistance.
The security vulnerability applies to the following combinations of products.
15.3M 15.3(100)M, 15.3(3)M, 15.3(3)M1, 15.3(3)M2, 15.3(3)M3, 15.3(3)M4, 15.3(3)M5, Base
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.