Cisco IOS Gigabit Switch Router (GSR) devices that are configured for Protocol Independent Multicast (PIM) contain a vulnerability that could allow an unauthenticated, remote attacker to cause the device to crash.
The vulnerability is due to an error that may occur when the devices process crafted PIM packets. An attacker could exploit the vulnerability by sending a crafted request to the affected system. An exploit could allow the attacker to cause the GSR device to crash, which may result in a denial of service (DoS) condition.
Cisco has confirmed the vulnerability in a security advisory and released updated versions.
The vulnerability exists when Cisco IOS software that is running on a GSR device is configured to process PIM packets. PIM is not enabled by default and must be enabled for a system to be vulnerable. Cisco IOS software does not properly process malformed PIM requests. The processing of a malicious request could cause a device to fail and restart.
An unauthenticated, remote attacker could exploit the vulnerability by crafting a malicious PIM request and sending it to an affected system. When the packet is processed, the system fails to properly handle the request. An exploit could allow the attacker to cause the affected router to reload, which may result in a DoS condition.
Limited information is available to describe this vulnerability. A single exploit could allow the attacker to cause the affected router to reload, which may result in a DoS condition. Repeated exploitation could allow an attacker to render a device completely unavailable.
Cisco indicated through CVSS scoring the existence of functional exploit code; however, this exploit code is not known to be publicly available.
Administrators are advised to apply the appropriate update.
Administrators may consider using access control lists (ACLs) to restrict packets that do not originate from authorized sources.
Administrators may consider allowing only trusted PIM neighbors to access the device.
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-20080924-multicast
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 email@example.com.
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Cisco Multivendor Vulnerability Alerts respond to vulnerabilities identified in third-party vendors' products. These alerts contain information compiled from diverse sources and provide comprehensive technical descriptions, objective analytical assessments, workarounds and practical safeguards, and links to vendor advisories and patches.