Cisco IOS contains a vulnerability that could allow an unauthenticated, remote attacker to bypass the configured encryption policy on a targeted device. Updates are not available.
A vulnerability in the Cisco Group Encrypted Transport VPN (GET VPN) feature of Cisco IOS could allow traffic to bypass the configured encryption policy.
The vulnerability is due to the default, implicit policies set in place to permit Group Domain of Interpretation (GDOI) traffic to flow unencrypted to allow the GET VPN group members (GMs) to communicate with the GET VPN key servers (KSs). Only transit or to the device traffic using UDP as the transport protocol and port 848 as either the source or destination will bypass the user-defined encryption policies.
Cisco has confirmed this vulnerability in a security notice; however, software updates are not available.
At the time this alert was first published, Cisco IOS versions 15.1(4)M8 and prior were vulnerable. Later versions of Cisco IOS may also be affected.
To exploit this vulnerability the attacker would likely need access to trusted, internal networks in which the targeted device may reside. Depending on the network configuration, such systems are typically placed behind network security devices, such as firewalls.
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-2013-3436
Customers should refer to Cisco bug ID CSCui07698 for the most complete list of affected product versions.
An unauthenticated, remote attacker could exploit this vulnerability to bypass the configured encryption policy on a targeted device. Successful exploitation could be used to gain access to sensitive information that could be leveraged to conduct further attacks.
The vulnerability is due to the default configuration on implicit policies to permit GDOI traffic to flow unencrypted, allowing the GET VPN GMs to communicate with the GET VPN KSs.
An unauthenticated, remote attacker utilizing UDP port 848 could exploit this vulnerability to bypass the user-defined encryption policies on the targeted device. Successful exploitation could allow the attacker the ability to gain access to sensitive information that could be leveraged to conduct further attacks.
Administrators are advised to contact the vendor regarding future updates and releases.
Understanding activity on the network provides information and visibility to help identify potential security incidents. Organizations are advised to log events from devices and review the data to discern anomalies or malicious activity. For logging best practices, see Cisco Guide to Harden Cisco IOS Devices.
To prevent information disclosure and unauthorized access, restrict privileged management access to devices. Apply security features such as Management Plane Protection or Control Plane Protection to the device. For best practices for securing interactive management sessions, see Cisco Guide to Harden Cisco IOS Devices.
Administrators are advised to review the workaround section described in the CSCui07698 bug details.
Administrators are advised to monitor affected systems.
Alerts and bulletins on the Cisco Security Intelligence Operations Portal are highlighted by analysts in the
Cisco Threat Operations Center and represent a subset of the comprehensive content that is available through Cisco Security IntelliShield Alert Manager Service.
This customizable threat and vulnerability alert service provides security staff with access to timely, accurate, and credible information about threats and vulnerabilities that may affect their environment.
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.