Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service condition. Updates are available.
Description
Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.
The vulnerability is in the Cisco Express Forwarding feature when a device is configured to use IP-based tunnels. An unauthenticated, remote attacker could exploit this vulnerability by sending crafted malformed packets to the affected device. Such requests could cause the system to reload, resulting in a DoS condition.
Cisco has confirmed this vulnerability and released updated software.
Warning Indicators
Cisco has published a list of affected Cisco IOS Software releases in the security advisory. The Vendor Announcements section of this alert contains a link to the advisory.
IntelliShield Analysis
Cisco devices that are using IP-based tunneling with Cisco Express Forwarding enabled are vulnerable. Cisco Express Forwarding is enabled by default on most versions of Cisco IOS Software. However, systems configured to use only Cisco multicast VPN (MVPN) for tunneling are not affected by this vulnerability.
Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.
An unauthenticated, remote attacker could exploit this vulnerability to cause the affected device to reload, resulting in a DoS condition. Repeated attacks could result in a persistent DoS condition.
Technical Information
Additional technical information is not currently available.
Safeguards
Administrators are advised to apply the appropriate updates.
Administrators may consider disabling Cisco Express Forwarding. This change will have an adverse effect on performance, however.
The Cisco Applied Intelligence team has created the following companion document to guide administrators in identifying and mitigating attempts to exploit this vulnerability prior to applying updated software: cisco-amb-20090923-tunnels
Patches/Software
Cisco customers with active contracts can obtain updates through the Software Center at the following link: Cisco. Cisco customers without contracts can obtain upgrades by contacting the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via e-mail at tac@cisco.com.
The security vulnerability applies to the following combinations of products.
Primary Products:
Cisco
IOS
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Associated Products:
N/A
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