Cisco IOS contains a vulnerability that could allow an unauthenticated, remote attacker to cause an affected device to stop processing network requests, resulting in a denial of service (DoS) condition.
The vulnerability is due to improper handling of malformed network packets. An attacker could exploit the vulnerability by sending a malicious network packet to the affected device. The processing of a malicious packet could trigger an error condition that causes the affected device to stop processing network requests, resulting in a DoS condition.
Cisco confirmed the vulnerability and released software updates.
Indicators of Compromise
Cisco has published a list of vulnerable IOS products in the advisory.
Only Cisco Catalyst 6500 Series or Catalyst 7600 Series devices containing a Supervisor Engine 32 (Sup32), Supervisor Engine 720 (Sup720), or Route Switch Processor 720 (RSP720) module may be vulnerable to an exploit. Additionally, only those devices running OSPF on interfaces with the sham-link option enabled and using the Multiprotocol Label Switching (MPLS) Virtual Private Networking (VPN) feature are vulnerable.
The vulnerability is due to improper handling of malformed network packets. Cisco IOS fails to properly process OSPF messages in certain circumstances in an affected configuration. The processing of a malformed message may cause the processing queue to become blocked, preventing the processing of additional packets and eventually resulting in the filling of the queue. The ultimate result would be a failure to process further network requests. The processing of a malformed packet may also cause the device to fail to properly free memory, resulting in the exhaustion of available memory resources. Each error condition could cause the device to stop processing network requests.
Because devices accept OSPF packets into the queue prior to authenticating the origin of the messages, attackers do not require special privileges or authentication to exploit this vulnerability. Depending on the site configuration, attackers may require access to internal network segments to send a malicious packet to the affected device.
Only very specific hardware and software configurations are affected by this vulnerability. Vulnerable targets may be difficult for an attacker to identify and exploit.
The CVSS score indicates that proof-of-concept code exists for this vulnerability; however, this code is not believed to be publicly available at this time.
Administrators are advised to apply the appropriate update.
Administrators may consider removing the OSPF Sham-Link configuration.
Administrators may consider increasing the Selective Packet Discard (SPD) value option to increase queue length.
Administrators may consider employing the Cisco IOS Embedded Event Manager to detect and respond to unresponsive devices.
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 firstname.lastname@example.org.
IntelliShield is re-releasing this alert to include common vulnerability identification information.
2008-April-02 12:30 GMT
Cisco IOS contains a vulnerability that could allow an unauthenticated, remote attacker to cause an affected device to stop processing network requests, resulting in a denial of service condition. Updated software is available.
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